Synonyms of the word

formerly

• adv. at some time in the past.
• adv. previously; once.

erst

• adj. (obsolete) First.
• adv. (obsolete) First of all, before (some other specified thing).
• adv. (obsolete) Sooner (than); before.
• adv. (archaic, poetic) Formerly, once, erstwhile.

erstwhile

• adv. Formerly; in the past.
• adj. (literary, law) Former, previous.
• adj. (proscribed) Respected, honourable.

once

• adv. (frequency) One and only one time.
• adv. (temporal location) Formerly; during some period in the past.
• adv. (mathematics) Multiplied by one: indicating that a number is multiplied by one.
• adv. As soon as.
• conj. As soon as; when; after.