Q: Recently I noticed that in Polish you say “wielu ludzi jest” and not “wielu ludzi są”. “Wielu” means “many” so why can’t we use the plural form of the verb?
A: “Wielu”, also known more colloquially as “wiele”, is an undefined numeral, and in this sentence is acting as a subject. In the Polish language we distinguish a few categories of subjects; in the case of the mentioned sentence we need to focus on two: grammatical and logical. Logically, “wielu” is associated with the plural, however grammatically “wielu” requires using the singular, and that is what we need to use in the sentence. A similar phenomenon occurs when using “dużo” and asking “ilu”/ “ile” (“how many”), e.g. “Ilu ludzi jest w pubie?” (“How many people are in the pub?”). Please note that this structure requires the genitive plural case when used with nouns, e.g. “dużo kobiet”, “wielu turystów” (“many women”, “many tourists”).