虫子 (chóng zi) literally combines 虫 (chóng), meaning 'insect' or 'creeping creature', and 子 (zi), a common diminutive or noun suffix that adds a colloquial, informal, or sometimes affectionate or mildly dismissive tone. Though 虫 alone can refer to insects or bugs in formal or scientific contexts, adding 子 makes the term more conversational and everyday — often used for small, crawling, or flying creatures people encounter casually, like ants, flies, spiders, or caterpillars. It’s not strictly limited to entomologically correct insects; in speech, it may loosely include worms, centipedes, or even tiny pests.

The word carries neutral-to-mildly negative connotations depending on context — it’s rarely used in formal writing or biology class, but very common in spoken Mandarin, especially among children or in casual descriptions of nature or household annoyances. Parents might say '别怕，这只是一只小虫子' ('Don’t be afraid, it’s just a little bug'), while someone spotting something creepy in their food might exclaim '哎呀，碗里有虫子！' ('Ah! There’s a bug in my bowl!').