perhaps
Synonym discussion
Sense: adverb/1
'Perhaps' and 'maybe' both show uncertainty, but 'perhaps' usually sounds a little more careful or formal. 'Possibly' is close in meaning, though it often appears in more planned or written English. 'Probably' is different because it shows a stronger belief that something is true or will happen. 'Conceivably' is rarer and suggests a weaker, more distant possibility, often one the speaker does not really expect. For everyday conversation, 'maybe' is often the easiest choice; for a slightly softer or more thoughtful tone, 'perhaps' fits well. Compare: 'Maybe Ben missed the bus' sounds casual, while 'Perhaps Ben missed the bus' sounds more measured. 'Ben probably missed the bus' shows much more confidence.
Etymology
Perhaps was formed in Middle English from 'per' and 'hap', an old word meaning 'chance' or 'luck'. The same old idea of chance also appears in words such as 'happen' and 'happy'. Over time the two parts came together as one word, and 'perhaps' became a common way to leave room for uncertainty.