say it: STURN-lee
sternly is an adverb meaning "with sternness; in a severe manner". It carries one recorded sense.
with sternness; in a severe manner
“`No,' she said sternly”
“peered severely over her glasses”
Definitions, synonyms and semantic relations for sternly come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.