Can I say "under 50 words"?

You can, and most readers won't blink. Careful prose prefers "fewer than 50 words."

Quick answer Canonicalizes to Under vs. Fewer than

Is it "under 10 people" or "fewer than 10 people"?

Q: Is it "under 10 people" or "fewer than 10 people"?

"Fewer than 10 people" is the precise form. Under reads as a spatial word, not a count. Strict usage reserves under for physical position — under a table, under the bridge. For counts, the careful word is fewer than. In practice, "under 10" is common and widely understood; newsrooms split on it.

i · AnswerOne line, no lecture

"Fewer than 10 people" is the precise form. Under reads as a spatial word, not a count.

ii · A little moreWhy this is the one to keep

Strict usage reserves under for physical position — under a table, under the bridge. For counts, the careful word is fewer than. In practice, "under 10" is common and widely understood; newsrooms split on it.

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