alternately
Alternately (adverb) means taking turns, one after the other in a repeating order. Example: “The traffic lights turned red and green alternately.”
How to use alternately
Learner’s notesIn plain EnglishDoing or being something in turns, one after another.
The turn-taking sense is standard everywhere, while the 'as another option' sense is more restricted and some readers consider it a mistake.
If you mean 'as another option', alternatively is the safer choice in formal writing.
Trace the full origin ↓Fill the gap
Can you complete this real example?
The traffic lights turned red and green _____.
Etymology
Alternately is built from the adjective alternate with the adverb-forming suffix -ly attached to it.