Euglena and Protozoon

Euglena noun - Minute single-celled green freshwater organism having a single flagella; often classed as algae.

Protozoon and euglena are semantically related. In some cases you can use "Protozoon" instead a noun "Euglena".

Protozoon noun - Any of diverse minute acellular or unicellular organisms usually nonphotosynthetic.

Euglena and protozoon are semantically related. Sometimes you can replace term "Euglena" with "Protozoon", this nouns are similar.