Alternately means first one and then the other, over and over. Alternately hot and cold, alternately amused and annoyed, work alternately.
It is worth keeping apart from alternatively, which means as another option — alternately means in turn and the two are constantly swapped. The pattern must be regular for the word to fit, so it names a rhythm rather than a mixture.
1adverbalternatelyFirst one and then the other, over and over.
“The weather was alternately sunny and rainy all week.”
alternately is an order.
Proto-Indo-European
*h₂el- (other)
Latin
alternātus
English
alternate
English, today
alternately
Built from
From alternate + -ly. alternate Latin alternātus, the perfect passive participle of Latin alternō (“to take turns”) (see -ate), from alternus (“one after another, by turns”), from alter (“other”) + -nus. a doublet of altern; see also alter.
Etymology from Wiktionary, CC BY-SA