unfortunately
The word 'leider' is an adverb in German that is used to express regret or disappointment. It is often used to introduce a negative statement or to express that something is not as one would have hoped or expected. For example, 'Leider habe ich meinen Schlüssel verloren.' means 'Unfortunately, I lost my key.' or 'Leider kann ich nicht kommen.' means 'Unfortunately, I cannot come.'.
Unfortunately, I cannot come today.
This phrase expresses regret; 'leider' suggests a feeling of regret or disappointment about the fact that the speaker cannot come.
Sadly, I have no time.
The term 'leider' is used to denote regret. The speaker wishes they had time but unfortunately they do not.
Regrettably, he is sick.
The term 'leider' here expresses an unfortunate or regrettable circumstance. The speaker expresses sympathy for the person who is sick.