They started as same word, but their meanings have drifted apart over time.
Editor Emily Brewster clarifies the difference.
A simple way to keep them apart. (Most of the time.)
We'll tell you all the perpendiculars
A simple trick to keep them separate
Many of today's grammar rules can be traced to the opinions of one 18th century writer.
'Poets laureate'? 'Court-martials'? The curious history of postpositive adjectives in English.
