Abbreviation for Cousin: How 1C, 2C, and 1C1R Actually Work

The standard abbreviation for cousin in genealogy is simply C, and it almost never appears alone. It carries a number in front of it for the cousin degree and, when needed, a number and an R behind it for removals. So 1C is a first cousin, 2C is a second cousin, and 1C1R is a first cousin once removed. That compact system covers every cousin relationship English can name, in four characters or fewer.

There is no formal dictionary abbreviation for the word "cousin" the way there is for "Mister" or "Avenue." What exists instead is a working shorthand that genealogists, DNA analysts, and family-tree software have converged on, plus the informal "cuz" that belongs to conversation rather than records.

The Abbreviation for Cousin, in One Line

Cousin is abbreviated C, preceded by the degree and followed by the removals: [degree]C[removals]R.

Read that formula from left to right and every notation you will meet decodes itself:

• 1C = first cousin
• 2C = second cousin
• 1C1R = first cousin once removed
• 2C1R = second cousin once removed
• 1C2R = first cousin twice removed
• 3C2R = third cousin twice removed
• 5C = fifth cousin

The first number is the cousin degree. The letter C stands for cousin. The second number counts removals, and the R stands for removed. No spaces, no punctuation, no capitalization variants that matter.

If you can read that formula, you can read almost any genealogy note, DNA Painter chart, cluster spreadsheet, or forum post about cousin relationships.

What Each Piece Actually Means

The two numbers in a cousin abbreviation measure two completely different things, and mixing them up is the source of nearly every misreading.

The degree number counts generations to the shared ancestor. It comes from the closer of the two people. Someone two generations below a shared couple, like a grandchild, produces first cousins. Three generations below produces second cousins. Take the number of generations and subtract one.

The removal number counts the generation gap between the two people. If both people sit at the same depth, there are no removals and no R appears at all. If one sits a generation lower, that is one removal. Two generations lower is two removals.

The two are independent. A first cousin four times removed is still a first cousin, because somebody in the pair is only two generations from the shared grandparents. The 4R is describing the vertical gap, not the closeness of the blood relationship. That independence is spelled out at length in 1st cousin 2x removed and 2nd cousin 1x removed, which are the two removed relationships people search for most.

The Full Abbreviation Table

Here is the shorthand in both directions, with the plain-English relationship and who the person is.

The bare C in the first row is worth a warning. Written by itself it tells the reader nothing: it could mean any cousin at any degree, and in handwritten notes it gets confused with other abbreviations entirely. Always attach the number, even when you think the context is obvious. Future you will not remember the context.

How Removal Gets Written

Removal has three common written forms, and they all mean the same thing.

The "1x removed" form is the newest of the three and shows up heavily in how people actually type their questions. It reads as "one times removed," which is not elegant English, but it is unambiguous and short, and it has stuck.

Two conventions to keep straight:

The R is redundant but expected. 1C1R could technically be written 1C1, but nobody does. The R prevents the two numbers from running together and makes the string readable at a glance.

Order is fixed. The degree always comes first. There is no notation where the removal number leads, so a string like R1C1 is not a thing you will encounter, and writing it will only confuse people.

Half Relationships: The H Prefix

A half relationship gets an H in front: H1C is a half first cousin, H2C1R is a half second cousin once removed.

Half cousins share one common ancestor rather than an ancestral couple. This happens when the person at the top of the tree had children with more than one partner. Half relationships share roughly half the DNA of their full equivalents, which is exactly why the H matters so much in DNA notes. An H1C and a 1C1R have similar expected sharing despite being completely different relationships, and losing the H turns a solvable puzzle into an unsolvable one.

You will occasionally see "Half 1C" written out, or "1/2 1C" in older material. All three mean the same thing. Pick one and use it consistently within a single document.

The Other Abbreviations on the Same Charts

Cousin shorthand rarely appears alone. It lives alongside a small vocabulary of related abbreviations, and knowing them makes relationship charts readable.

Two of those need care. The great-grandparent abbreviations are written inconsistently across the hobby: some people count the "greats" and write GGGP, others use a multiplier and write 2xGGP for the same person. Those two notations describe an identical ancestor by different counting habits, and mixing them in one document is a reliable way to lose track of a generation. Pick one style.

The other is MRCA, which is the single most useful abbreviation in genealogy. Every cousin relationship is defined by the MRCA, and if you cannot name the MRCA, you cannot name the relationship. The free calculator at cousinchart.com works from exactly that principle.

How DNA Companies Label Matches

Consumer DNA sites mostly do not use the abbreviation for cousin. They spell relationships out, and they give ranges rather than single answers.

Ancestry writes relationships in full, like "1st cousin once removed," and groups matches into buckets such as "Close Family," "2nd Cousin," and "Distant Cousins." Its predictions come with a list of possible relationships behind them.

23andMe also spells out predictions, showing things like "2nd Cousin" or "3rd to 4th Cousin," with a percentage of shared DNA alongside.

MyHeritage and Family Tree DNA use similar written ranges, typically a span like "2nd–4th cousin."

Community tools are where the shorthand lives. DNA Painter's Shared cM Project tool, cluster spreadsheets, chromosome-mapping notes, and genealogy forums all run on 1C1R and 2C2R, because those tools display dozens of relationships at once and need them to fit in small boxes.

So the practical situation is this: you will read the full names on the testing site, then translate them into shorthand the moment you start taking your own notes. Everyone does this, which is why the notation exists.

One caution about DNA labels. A company's prediction is generated from a centimorgan total, and different relationships produce overlapping totals. A match labeled "2nd cousin" might be a 2C, a 1C2R, or an H1C1R, all of which average about the same amount of shared DNA. The abbreviation you eventually write in your notes should reflect the relationship you have documented, not the one the site guessed.

Cuz, Cus, and the Informal Forms

"Cuz" is the informal abbreviation for cousin in speech and casual writing. It is not genealogy notation and should never appear in a family tree.

You will also see "cus" and, less often, "coz," which is the older spelling and turns up in Shakespeare and in nineteenth-century letters. All three are affectionate address terms rather than relationship labels. They tell you nothing about degree or removal, and in many families they are used for people who are not blood relatives at all.

Other varieties of English handle the informal register differently. In South Asian English, "cousin brother" and its shortened form "cousin bro" specify a male cousin, adding information that American English leaves out entirely. That usage, and the reasons behind it, are explained in cousin bro.

Cousin Abbreviations in Old Records

Historical documents abbreviate cousin inconsistently, and the word itself meant something looser than it does now.

Two separate problems come up when you meet "cousin" in an old will, letter, or census page.

The abbreviation was never standardized. Clerks and enumerators wrote what fit the space and what their own training suggested. You will find the word written in full, truncated with a period, or contracted in ways that depend entirely on the individual writer's hand. There is no lookup table that decodes them all, and treating a particular form as a fixed standard will lead you wrong.

The word covered more ground. Through much of the seventeenth, eighteenth, and nineteenth centuries, "cousin" was used broadly for kin in general. Wills routinely called nephews, in-laws, and vaguely connected relations "cousin." So even a fully spelled-out "cousin" in an old document is a starting point for research, not a determination of the relationship.

The modern shorthand is a product of twentieth-century genealogy and DNA testing, where precision suddenly mattered a great deal. Reading it back into older records is an anachronism.

Writing Cousin Abbreviations Well

Consistency matters more than which convention you pick. Four habits keep notes readable years later.

Always include the degree number. Never write a bare C. 2C takes one extra character and removes all ambiguity.

Note the direction of removals separately. The abbreviation for cousin with removals, like 1C1R, does not say which person is older. Add a word: "1C1R (up)" or "1C1R via Grandma Ruth" makes the note self-explanatory. This is genuinely important, because the older-generation and younger-generation versions of a removed relationship are equally common and completely different research targets. The problem is easy to see in practice with what is your mother's cousin to you, where the same 1C1R label covers a great-aunt-aged relative and a toddler.

Name the MRCA alongside the abbreviation. "3C via John & Mary Palmer" is worth ten times more than a bare 3C, especially in a DNA spreadsheet where you will eventually be sorting hundreds of matches by ancestral line.

Add uncertainty markers. A question mark or a "prob." in front of a hypothesized relationship keeps guesses from hardening into facts. At distant degrees this is essential, because a 5th cousin label is nearly always a hypothesis rather than a proven relationship.

Frequently Asked Questions

What is the abbreviation for cousin?

In genealogy it is C, written with the degree in front, so 1C is a first cousin and 2C is a second cousin. Removals are added as a number plus R, giving forms like 1C1R for first cousin once removed. In casual speech, "cuz" is the informal abbreviation.

What does 1C1R mean?

First cousin once removed. The 1 before the C is the cousin degree, the C stands for cousin, and the 1R means one generation of separation between the two people.

Is there an official abbreviation for cousin in English?

No. Unlike titles and street types, "cousin" has no standard dictionary abbreviation. The C-based notation is a genealogy convention that became standard through use rather than through any governing body.

How do you abbreviate half cousin relationships?

With an H prefix, so H1C is a half first cousin and H2C1R is a half second cousin once removed. Some writers use "Half 1C" instead. Both are understood, but keep one style throughout a document.

Do DNA testing sites use these abbreviations?

Mostly not. Ancestry, 23andMe, MyHeritage, and Family Tree DNA spell relationships out and give ranges. The shorthand appears in community tools like the Shared cM Project charts, cluster spreadsheets, and forum discussions.

Does 1C1R tell you who is older?

No, and this is its main weakness. The same abbreviation covers your parent's first cousin and your first cousin's child. Add a note about direction or name the connecting relative whenever you write it down.