n. 1
The state of being extremely friendly; intimacy.
n. 2
Undue intimacy; inappropriate informality, impertinence.
n. 3
An instance of familiar behaviour.
n. 4
Close or habitual acquaintance with someone or something; understanding or recognition acquired from experience.

Forms

Plural: familiarities → intimacies, closenesses, nearnesses, friendships…

Choose the right word

Familiarity, Acquaintance or Intimacy?

Acquaintance admits of many degrees, from a slight or passing to a familiar or intimate acquaintance; but acquaintance unmodified commonly signifies less than familiarity or intimacy.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

friendship Friendship is a plant which must be often watered.
intimacy Yanni and Skura want to have moments of intimacy.
closeness I don't fear the closeness between different peoples.
knowledge Anna married without the knowledge of her parents.
acquaintance I made her acquaintance through his introduction.

Popularity over time

Word	1850 → 2019	Trend
familiarity		rising
friendship		steady
intimacy		rising
closeness		rising
nearness		steady
knowledge		rising

Use in printed books, per decade from 1850 to 2019.

By length

7 letters: liberty³
8 letters: intimacy⁴, nearness
9 letters: knowledge², closeness², indecorum
10 letters: friendship², fellowship³, casualness⁴, affability
11 letters: intercourse³, impropriety⁵, informality⁵, conversance, conversancy
12 letters: conversation⁴, acquaintance³, friendliness³, unconstraint

The small number after each word is its number of syllables (liberty³ = 3 syllables).

In other languages

Français: familiarité
Italiano: familiarità
Español: familiaridad
Deutsch: Vertrautheit