Is it cockroach or roach?

Both cockroach and roach refer to the same insect, with cockroach being the formal common name and roach being a shortened informal version, so both are correct and interchangeable in everyday language, though cockroach is preferred in scientific and professional contexts. The insect belongs to order Blattodea, with common species including German cockroach which is small light brown about half an inch with two dark stripes common in kitchens, American cockroach which is large reddish brown about one and a half inches often called palmetto bug that lives in drains and basements, and Oriental cockroach which is dark brown. Entomologists and pest control professionals typically use cockroach in reports and treatment plans because it is more precise and avoids confusion with other insects like wood roaches. Roach is simply a colloquial shortening commonly used in everyday speech, as in I saw a roach in the kitchen, and is widely understood. Some people mistakenly think roach refers only to small species and cockroach to large, but there is no taxonomic difference, roach is just slang. In pest control industry, you will see both terms used, with product labels often saying cockroach killer and people saying roach killer. So whether you say cockroach or roach, you are referring to same pest that carries bacteria, triggers allergies, and requires integrated pest management including sanitation, sealing cracks with caulk, and gel baits containing fipronil to eliminate colonies. If writing formally, use cockroach, if speaking casually, roach is fine.