I heard one of these adjectives this morning and wondered why the speaker did not use the other.

Question:
Do these two adjectives mean the same thing?

Explanation:
I was watching “Landscapers’ Challenge” on the HGTV channel and heard a designer say something to the effect of “You need a pot that is proportionate to the size of the plant.”

The adjective “proportionate” in her statement struck me as odd because I would have used the adjective “proportional” instead.

Both adjectives date back to late 1300s.

If you look up the definition of “proportionate”, then you will see that one of its definitions is proportional.

In contrast, if you look up the definition of “proportional” in many dictionaries, then you will not see that one of its definitions is proportionate, although “proportionate” is listed as a synonym of “proportional”.

One of the primary definitions of both adjectives is being in proportion.

So these two adjectives essentially mean the same thing.

For fun, and because I was curious about which adjective was more popular on the Web, I searched Google for each of these adjectives and got about the indicated numbers of matches:

• “proportional” — 32,100,000 matches
• “proportionate” — 4,110,000 matches

This tells me that Web authors have favored “proportional” over “proportionate” by a ratio of 7.81-to-1, which is consistent with my initial reaction to hearing “proportionate” in the HGTV program.

Answer:
The two adjectives mean essentially the same thing, but “proportional” seems to be much more popular than “proportionate”.