populace / populous / populus are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
populace: (noun) people in general considered as a whole.
populous: (adjective) densely populated.
populus: (noun) a genus of trees of the family Salicaceae that is found in the northern hemisphere; poplars.
populace: p·AA·p·y·ah·l·ah·s
populous: p·AA·p·y·ah·l·ah·s
populus: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)