不好意思，我忘了

The phrase '不好意思' (bù hǎo yì si) is a common expression in Mandarin Chinese used to express embarrassment, apology, or shyness. '不' (bù) means 'not' or 'no'. '好' (hǎo) means 'good' or 'well'. '意思' (yì si) means 'meaning', 'idea', 'opinion', or 'intention'. When put together, '不好意思' literally translates to 'not good meaning' or 'it's not a good intention/idea', which colloquially conveys a sense of being apologetic, embarrassed, or feeling a bit awkward about something. It's a milder form of apology than a direct '对不起' (duì bu qǐ - I'm sorry). It can also be used to politely decline an offer, interrupt someone, or ask for a favor. '我' (wǒ) means 'I' or 'me'. '忘' (wàng) means 'to forget'. '了' (le) is a particle indicating a completed action or a change of state. So, '我忘了' (wǒ wàng le) means 'I forgot' or 'I have forgotten'. Combined, '不好意思，我忘了' (bù hǎo yì si, wǒ wàng le) directly translates to 'Excuse me / Sorry, I forgot.' It's a very common and polite way to apologize for forgetting something, often used in casual and semi-formal contexts. The '不好意思' softens the apology and shows a degree of mild regret or embarrassment about the oversight.