Synonyms of informal
1 naturalDictionary • She is refreshingly informal.
relaxed • The atmosphere at lunch was relaxed.
familiar • the comfortable, familiar atmosphere
unofficial • Rail workers have voted to continue their unofficial strike.
laid-back • Everyone here has a really laid-back attitude.
easy-going • They have a very easy-going attitude to life.
colloquial • He converses in colloquial Japanese as easily as in English.
2 relaxedDictionary • The house has an informal atmosphere.
relaxed • Try to adopt a more relaxed manner.
easy • She laughed and joked and made easy conversation with everyone.
comfortable • A home should be comfortable and friendly.
cosy • a cosy chat between friends
leisurely • Lunch was a leisurely affair.
3 casualDictionary • Most of the time she needs informal clothes.
casual • I bought casual clothes for the weekend.
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casualCasual clothes are ones that you normally wear at home or on holiday, and not on formal occasions.
• I bought casual clothes for the weekend.
colloquialColloquial words and phrases are informal and are used mainly in conversation.
• He converses in colloquial Japanese as easily as in English.
comfortableIf a building or room is comfortable, it makes you feel physically relaxed when you spend time in it, for example because it is warm and has nice furniture.
• A home should be comfortable and friendly.
Thesaurus for informal from the Collins English Thesaurus
not of a formal, official, or stiffly conventional nature