foster sister: meaning, definition, pronunciation and examples

C1
UK/ˈfɒstə ˌsɪstə/US/ˈfɑːstər ˌsɪstər/

Neutral to formal, often used in social work, legal contexts, and personal narratives.

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Quick answer

What does “foster sister” mean?

A girl or woman who is not a biological sibling, but with whom one is raised, having been brought up in the same foster family.

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Pronunciation

Definition

Meaning and Definition

A girl or woman who is not a biological sibling, but with whom one is raised, having been brought up in the same foster family.

More broadly, a female with whom one shares a significant formative upbringing in a non-biological family context, often implying a close, sibling-like bond formed through shared care and living environment.

Dialectal Variation

British vs American Usage

Differences

Term is used in both variants with identical meaning. The concept and legal framework of foster care are similar, though administrative terminology may differ regionally.

Connotations

Generally neutral. May carry connotations of resilience, chosen family, or a difficult background depending on context.

Frequency

Low-to-medium frequency in both, appearing primarily in specific contexts like social services, literature, or personal stories. Not part of everyday vocabulary for most.

Grammar

How to Use “foster sister” in a Sentence

[Possessive Pronoun/Name] + foster sistergrew up with + [as] + (her) foster sister

Vocabulary

Collocations

strong
myherhisformerchildhood
medium
closebelovedonlyolderyounger
weak
long-lostdearbiologicaladoptive

Examples

Examples of “foster sister” in a Sentence

adjective

British English

  • Their foster-sister relationship was incredibly strong.
  • She attended the foster sister support group.

American English

  • Their foster sister bond was incredibly strong.
  • She attended the foster sister support group.

Usage

Meaning in Context

Business

Not used.

Academic

Used in sociology, psychology, social work, and law papers discussing family structures, child development, and kinship.

Everyday

Used when explaining family relationships, especially in families formed through foster care.

Technical

Precise term in social work, child welfare, and legal documents concerning guardianship and family law.

Vocabulary

Synonyms of “foster sister”

Neutral

foster sibling (female)

Weak

non-biological sisterward sister (archaic/contextual)

Vocabulary

Antonyms of “foster sister”

biological sisterblood sisterfull sister

Watch out

Common Mistakes When Using “foster sister”

  • Using 'adoptive sister' interchangeably (adoption is permanent legal transfer of parental rights, fostering is often temporary care).
  • Using 'step-sister' (which implies a parent's marriage, not state/care system placement).
  • Omitting the possessive (e.g., saying 'She is foster sister' instead of 'She is my foster sister').

FAQ

Frequently Asked Questions

Typically, no. The legal relationship is with the foster parents, not between foster children. However, they may be considered part of the same 'foster family' for care purposes.

Yes. The term is used lifelong to describe the relationship formed during a shared foster childhood, regardless of current age.

A foster sister is a co-resident in a temporary or state-care family setting. An adopted sister is legally made a permanent daughter of your parents, severing legal ties with her birth parents. You can be adopted into a family with an existing foster child, making her your foster sister.

Generally not unless it's used as a proper noun or direct form of address, e.g., 'This is my Foster Sister, Jane' is less common. Usually: 'This is my foster sister, Jane.'

A girl or woman who is not a biological sibling, but with whom one is raised, having been brought up in the same foster family.

Foster sister is usually neutral to formal, often used in social work, legal contexts, and personal narratives. in register.

Foster sister: in British English it is pronounced /ˈfɒstə ˌsɪstə/, and in American English it is pronounced /ˈfɑːstər ˌsɪstər/. Tap the audio buttons above to hear it.

Learning

Memory Aids

Mnemonic

Think of FOSTER as 'for a short/long term' care, and SISTER as the familial role. A 'foster sister' is a sister you gain through being fostered in the same home.

Conceptual Metaphor

FAMILY IS A STRUCTURE (foster relationship is a constructed part of that structure). BOND IS GLUE (the bond is adhesive, not inherent).

Practice

Quiz

Fill in the gap
Even after leaving care, Maria remained close with her , with whom she had shared a home for seven formative years.
Multiple Choice

What is the key factor defining a 'foster sister' relationship?