Partial means only part of the whole. A partial refund, partial success, a partial eclipse.
The second sense is biased — a partial account, a partial judge — which is why impartial means fair. That pair is worth learning together, because partial and impartial look like opposites and one of them is about completeness and the other about fairness. Partial to something means fond of it: I am rather partial to a good pear. Note partially, which means to some extent.
1adjectivepartialOnly part of the whole.
“They offered a partial refund of about a third.”
2adjectivebiasedBiased towards one side.
“It is a partial account and it does not pretend otherwise.”
3adjectivefondFond of something.
“She is rather partial to a good crossword.”
partial is a quality of incompleteness or bias.
Latin partialis comes from pars, a part. The biased sense arose because taking a part means taking a side, and English kept both meanings from Old French, where the split had already happened.
Latin
partiālis — of or pertaining to a part
Old French
parcial — biased or particular
Middle English
partiall
English, today
partial
From Middle English partiall, parcial, from Old French parcial (“biased or particular”), from Latin partiālis (“of or pertaining to a part”), from Latin pars (“part”).
Etymology from Wiktionary, CC BY-SA