Could you please suggest whether it is correct to use the phrase "that is"
with the meaning "for example" or "to be precise" when it is followed by
an item list. For instance,

"The effect in induced by several groups of factors, that is external
factors, internal factors, and whatever else factors."

The expression "that is" with the designated meaning seems to be
idiomatic, so it probably won't retain it's idiomatic meaning if it is changed
into "that are". But in the same time using "is" before a list of items seems
gramatically incorrect.

Any ideas on whether the provided sentence is correct or what are
possible grammatically correct equivalents?

Thanks in advance.


The expression is fine - idiomatic, as you say. I guess it's also an idiom.

Your question about changing it to "that are," is amusing. Never thought of that! Emotion: smile

If you think of it as "for example" or "to be precise," the number issue seems to go away.

The reason we use singular "is," I believe, is that "that" is singular, referring to the previous statement, "statement" being singular.

If you were talking about TWO previous statements, I suppose you'd say, "those are," but, thank God, we never say that.

Anyway, let's call it a fixed idiom, so we don't have to change it!
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Hi Avangi,

> Anyway, let's call it a fixed idiom, so we don't have to change it!

Thanks, that is a relief.


As an aside, note the difference between "that" as a demonstrative pronoun and "that" as a relative pronoun:

Where is the item that is on sale? Where are the items that are on sale. (relative)

That is the item which is on sale. These are the items which are on sale. (demonstrative)