In morphology (of the linguistic variety), a blend is a word formation process created by combining part of one word with part or whole of another.

Most typically, a blend will take the first part of the first word and the last part of the last word, as in:
infotainment: information + entertainment
brunch: breakfast + lunch
smog: smoke + fog

However, there are other ways blends are formed, such as:
TriBeCa: Triangle + Below + Canal (Street)
hazmat: hazardous + materials
Fortran: Formula + Translator

Sometimes a blend will contain an entire word; only one of the words needs to be in partial form for a word to be considered a blend:
rebar: reinforced steel + bar
cranapple: cranberry + apple

However, spelling conventions (which are notoriously arbitrary and misleading in English) sometimes leads people to falsely believe that certain words are blends (e.g. weblog {web + log}). However, because no word appears only in partial form, these are actually compounds.