The word 'tropical' originates from the Greek tropikos, which relates to a turning, specifically the turning point of the sun at the solstices. This term was applied in geography to the two circles of latitude (the Tropics of Cancer and Capricorn) where the sun appears directly overhead at a solstice and appears to "turn back". Over time, the adjective evolved from describing these astronomical lines to characterizing the hot, humid climate found in the geographical zone between them. Thus, the modern meaning of 'tropical' as "pertaining to the hot regions near the equator" is a semantic extension from its original reference to the sun's turning points.

Structure: trop (turn) + ical (adjective suffix) - trop: From Greek tropikos, from tropē meaning "a turning, change". In this word, it refers to the point where the sun "turns back" at the solstices. - ical: A common English adjectival suffix derived from Latin -icalis, indicating "pertaining to" or "of the nature of".