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Plural of Sister-in-Law: Exploring the Correct Grammar in American English

plural of sister in law

Greetings! Today, I will delve into a topic that often sparks confusion among writers in American English: the plural of sister in law. It’s important to use the correct grammar to ensure clarity and accuracy in your writing. Let’s explore the correct plural form and shed some light on this grammatical conundrum.

According to reputable sources, such as the Cambridge English Corpus, the correct plural form of sister-in-law is “sisters-in-law.” This plural form takes into account the unique relationship that sisters-in-law share in the English language. However, it’s worth noting that colloquial usage may sometimes include the incorrect form “sister-in-laws,” as stated in Wiktionary.

Now that we have a better understanding of the correct plural form, let’s move on to exploring the definition and usage of sister-in-law in American English.

The Singular and Plural of Sister-in-Law


The plural of “sister-in-law” is “sisters-in-law.” This transformation from singular to plural might seem straightforward, yet it often causes confusion. The key is in understanding which part of the compound noun needs to be pluralized.

sister-in-law image

Understanding Sister-in-Law

Definition of Sister-in-Law

A sister-in-law is a woman who becomes a part of your family through marriage. This relationship can be established in two primary ways: she is the wife of your brother, or she is the sister of your spouse. Despite not being related by blood, a sister-in-law is often considered an integral member of the family.

Usage of Sister-in-Law

The term is used to signify a specific family relationship that is recognized legally and socially. It’s a term that finds its relevance in both legal documentation and social interactions.

Use of Sister-in-Law in Sentences

  1. My brother’s wife: “My sister-in-law, Emma, organized a surprise birthday party for my brother.”
  2. My spouse’s sister: “I went shopping with my sister-in-law, Ava, to pick out a gift for our parents’ anniversary.
  3. Legal context: “In the will, my brother named his sister-in-law as one of the beneficiaries.”
  4. Social context: “At the family reunion, my sisters-in-law and I prepared the barbecue.
  5. Cultural nuances: “In some cultures, a sister-in-law is treated with the same respect and closeness as a biological sister.”

Common Mistakes and Confusions

  • Misplacement of the plural: A common error is saying “sister-in-laws” instead of the correct “sisters-in-law.” The plural form applies to ‘sisters’ because it’s the subject of the compound noun.
  • Confusing the relationship: Sometimes, people may mistakenly use “sister-in-law” to refer to the wife of a spouse’s brother. However, this is the correct usage, as both the wife of a brother and the sister of a spouse are considered sisters-in-law.

Commonly Asked Questions

  • Q: Can “sister-in-law” refer to more than one person at the same time?
    • A: Yes, you can have multiple sisters-in-law if you have more than one brother who is married or if your spouse has multiple sisters.
  • Q: Is there a different term for a spouse’s sister and a brother’s wife?
    • A: No, in English, both relationships are referred to as “sister-in-law.
plural form of sister in law


Understanding the plural form of “sister-in-law” is essential for correct communication in a family context. This term not only defines a legal or social relationship but also carries the weight of familial bonds and responsibilities. Correct usage of “sisters-in-law” reflects one’s grasp of English language nuances and respect for family relationships.


What is the correct plural form of sister-in-law?

The correct plural form is “sisters-in-law.”

Is “sister-in-laws” a grammatically correct plural form?

No, “sister-in-laws” is not considered grammatically correct, although it may be used colloquially by some.

What is the definition of sister-in-law?

Sister-in-law refers to a female relative who is connected through marriage. It can refer to the sister of one’s spouse, the wife of one’s brother, or the sister of the spouse of one’s sibling.

What is a co-sister-in-law?

A co-sister-in-law refers to the wife of one’s sibling-in-law.

How do you pluralize sister-in-law correctly?

The correct way to pluralize sister-in-law is by using the form “sisters-in-law.”

What are some cultural references and examples of sisters-in-law?

Sisters-in-law may engage in competition regarding who can have the most children. They can also be united in caring for the children they have together. In some cultures, sisters-in-law work together, supporting each other in their shared responsibilities.

Jessica Smith

Jessica Smith

Jessica Smith, writer at, blends creativity with insight, exploring technology, culture, and psychology. With a background in English Literature, she crafts engaging stories inspired by nature and urban life. Outside writing, she enjoys exploring and continuous learning.View Author posts

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