Paronyms are words that are pronounced or written in a similar way but which have different lexical meanings. Paronyms contrast with homonyms, which are words with different meaning having the same pronunciation or spelling. Examples of paronyms include:

alternately and alternatively

collision and collusion

conjuncture and conjecture

excise and exercise

prolepsis and proslepsis

continuous and contiguous

affect and effect

upmost and utmost

deprecate and defecate

paronym and paronorm

Some paronyms are truly synonymous, but only under the rarest of conditions. They often lead to confusion.

The term paronym can also refer to words that are derived from the same root, i.e. cognate words.

More Info: en.wikipedia.org