How to say "underside" in Japanese

Choosing the right word

下側したがわCommon
no-adjectiveThe general sense of 'underside': the lower side of something, the part facing down. The common all-purpose choice for locating what is beneath, as with a desk or a car.
しかもメモの下側したがわにあるのは汚よごれじゃなく・・・け、血判けっぱん！？↗
Moreover, what's on the bottom of the memo isn't dirt but a ... b-blood seal!?
底面ていめん
nounRefers to the bottom surface of an object — the face forming its base — so it fits 'bottom' and 'base' as well as 'underside', as when describing a box or appliance. Less common than 下側.
下面かめん
nounDenotes the undersurface of something and can also convey 'inferior surface' — the lower of two surfaces, as of a part or structure. Less common than 下側.

For the underside in general, 下側 is the common choice; the less common 底面 and 下面 name the bottom or undersurface as a specific surface of an object.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

Japanese equivalents

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