だってI heard/was said, Because, But, Even or also, Even if or even though

Both ときいた and だって express hearsay, but differ in tone and formality. ときいた means 'I heard that (A)' and is neutral and conveys information directly heard by the speaker, while だって is casual and emphatic, often used in conversation to mean something like 'They say (A).' or 'I'm telling you (A).'.

だって and それでも both express contradiction. だって is casual and often used at the start of a sentence to offer an objection, e.g., だって疲れたもん ('But I'm tired!'). それでも is less casual and shows contrast with a neutral tone, e.g., 雨だった。それでも行った ('It was rainy, but I still went.').

Both expressions involve だって, but their usage differs. んだって appears at the end of a sentence and means 'I hear (A)' or 'they say (A)', with an explanatory nuance added by ん. In contrast, だって is more flexible. It can appear at the beginning, middle, or end of a sentence, and has several meanings. It can function as a casual 'because', 'even though', or 'they say (A)', depending on context.

These are two expressions that can look very similar, or even identical in some cases, as たって when used with nouns will become だって. As an overall guideline, だって is a casual expression used to express 'I hear (A)' or 'they say (A)', or as a colloquial 'because', while たって is one way to say 'even though (A)' or 'even (A)', similar to ても or でも.

Both can be used to report hearsay (i.e. 'they say (A)'), but differ in tone and nuance. ということだ is more formal and can carry the nuance of summarizing or confidently reporting what the speaker heard. だって is much more casual and light, and can also be used at the beginning of a sentence with an emphatic 'but I mean (A)' nuance, which is something ということだ cannot do.

Both can be used to express reasons, but だって is highly casual, colloquial, and emotional, while なぜなら〜から is formal and objective-sounding. Also, なぜなら〜から begins a sentence, and clearly introduces a reason for something just stated, while だって can be used in sentence-final position. Depending on usage, だって can also have the meanings of 'I hear' and 'even though', which なぜなら〜から does not have.