Solution

ENTITIES

3 clues

Beings

Word class: Common noun
Nature of clue: Synonym
Difficulty: Easy
Sources: Boatload Puzzles
Topics: Philosophy

Things

Word class: Common noun
Nature of clue: Synonym
Difficulty: Very easy
Sources: Boatload Puzzles

Other solutions to Things

Units

Word class: Common noun
Nature of clue: Synonym
Difficulty: Easy
Sources: Boatload Puzzles
Topics: Numbers - Quantity - Units - Size

Other solutions to Units

Words are categorized by artificial intelligence: there can be mistakes.