Biology noob here, trying to expand his basic scientific knowledge.

<https://en.wikipedia.org/wiki/Unicellular_organism>

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> A unicellular organism, also known as a single-celled organism, is an
> organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells.
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But to me, this is ambiguous. Is a unicellular organism one that contains one cell and one cell only? Or is a unicellular organism one that contains one *kind* of cell, but lots of copies of that cell? So for example, are plants *not* unicellular because they contains groups of different types of cell, or are plants not unicellular simply because plants contain *more than one cell*?