frighten to make somebody feel afraid, often suddenly: He brought out a gun and frightened them off. scare to make somebody feel afraid: They managed to scare the bears away.
FRIFHTEN OR SCARE? Both are very common words, and are very similar, so you can use either one correctly. Scare is slightly more informal than frighten.
alarm to make somebody anxious or afraid: It alarms me that nobody takes this problem seriously.
FRIGHTEN OR ALARM? The subject of alarm is usually a thing, an event or a situation rather than a person. It is used to describe a feeling that something unpleasant or dangerous is going to happen in the future, and the feeling is often more one of worry than actual fear.
intimidate to frighten or threaten somebody so that they feel nervous or so that they will do what you want: They were accused of intimidating people into voting for them. startle to make somebody feel suddenly frightened or surprised, usually because of something sudden or unexpected: A sudden noise startled her.
PATTERNS AND COLLOCATIONS • Stop it! You're frightening/scaring me! • Oh sorry. I didn't mean to frighten/scare/startle you. • to frighten/scare somebody/something away/off • I was frightened/scared/alarmed/intimidated/startled by what he said. • He frightened/scared/intimidated me into telling him what happened.