Entomology is the study of insects.
More than one million different species of insect have been described to date.
They are the most abundant group of animals in the world and live in almost every habitat.
Insects have lived on earth for more than 350 million years.
entomology, branch of zoology dealing with the scientific study of insects.
The Greek word entomon, meaning “notched,” refers to the segmented body plan of the insect.
The zoological categories of genetics, taxonomy, morphology, physiology, behaviour, and ecology are included in this field of study.
entomology/ etymology
They sound similar and both end in -logy, which means "the study of," but don't mix them up unless you like completely confusing people.
Remember, entomology is the study of insects, like ants.
If you're talking about words and where they came from, use etymology.