How do you use alack in a sentence?

"Alack" is an archaic word meaning "alas" or "woe is me." It's rarely used in modern English, but you might see it in older literature or poetry. Here's an example of how you could use it:

Alack, my love, what have you done?

This sentence would be more typical of a Shakespearean play or a poem from a bygone era. In contemporary English, you'd likely say "Alas, my love, what have you done?" or "Oh no, my love, what have you done?"