Hookworm and Roundworm

Hookworm noun - Parasitic bloodsucking roundworms having hooked mouth parts to fasten to the intestinal wall of human and other hosts.

Roundworm and hookworm are semantically related. In some cases you can use "Roundworm" instead a noun "Hookworm".

Roundworm noun - Unsegmented worms with elongated rounded body pointed at both ends; mostly free-living but some are parasitic.

Hookworm and roundworm are semantically related. Sometimes you can replace term "Hookworm" with "Roundworm", this nouns are similar.