なくて details
write + not… and
kaka nakute
not… and; because (one) doesn't
朝、目覚ましが鳴らなくて、遅刻しちゃったよ。
asa, mezamashi ga naranakute, chikoku shichatta yo.
My alarm didn't go off this morning, so I ended up late. casual
質問の意味が分からなくて、もう一度聞き返した。
shitsumon no imi ga wakaranakute, mou ichido kikikaeshita.
I didn't understand the question, so I asked again. neutral
Examples
didn't/couldn't…, so — a negative clause linked to the feeling or result it causes
朝、目覚ましが鳴らなくて、遅刻しちゃったよ。
asa, mezamashi ga naranakute, chikoku shichatta yo.
My alarm didn't go off this morning, so I ended up late. casual
質問の意味が分からなくて、もう一度聞き返した。
shitsumon no imi ga wakaranakute, mou ichido kikikaeshita.
I didn't understand the question, so I asked again. neutral
すぐにご連絡できなくて、申し訳ございませんでした。
sugu ni go renraku dekinakute, moushiwake gozaimasen deshita.
I am very sorry that I could not contact you sooner. formal
Formation
{V-nai-stem}なくてattaches to ない-stem
Notes
Related patterns
Similar
Both hand over a reason — なくて is the negative clause's own て-link, loose and often trailing into feeling (行けなくて残念), while ので wraps a full clause of either polarity into an explicit because.
Lookalikes
Both open with the ない-form, but ないで hangs its clause on the following verb as manner (食べないで出かけた — went out without eating), while なくて closes it off as a reason (食べられなくて残念); each usually sounds wrong in the other's slot.
なくて alone links a reason or contrast ("not doing, so…"); adding もいい turns it into an exemption — the shared なくて opening invites misreading mid-sentence.