Basic expressions: Greeting someone and apologizing for being late

🇯🇵 [ごめん] is casual and is fine with friends, family, or people close to you. For strangers, coworkers, or anyone you want to sound more polite with, [ごめんなさい] is safer.

💬 This comes from [おくれる], "to be late," and [ました] makes it polite and puts it in the past: literally "was late." Japanese often uses this past form for a situation that has already happened when you arrive, like [おそくなりました] too.

🇯🇵 [だいじょうぶだよ] is friendly and reassuring, something you'd say to someone you know or in a relaxed moment. With strangers or in a more polite setting, [だいじょうぶです] sounds more natural.

💬 [ほんとうに] is an adverb, so you can put it before lots of things to mean "really" or "truly": [ほんとうにありがとう], [ほんとうにいい].

🇯🇵 [ごめんなさい] is a more polite, fuller apology than casual [ごめん]. It works well in everyday situations when you want to sound sincere without being stiff.

💬 [〜しないで] is a common way to say "don't do …": here [きにする] becomes [きにしないで], "don't worry about it / don't mind it." You'll see the same pattern in [わすれないで] ("don't forget").