underclay

As nouns the difference between terms and underclay

is that terms is while underclay is (geology) a stratum of clay lying beneath a coal bed.

As nouns the difference between underclay and underplay

is that underclay is (geology) a stratum of clay lying beneath a coal bed while underplay is the act of underplaying.

As a verb underplay is

to play in a subordinate, or in an inferior manner; to underact a part.

As nouns the difference between underlay and underclay

is that underlay is a layer (of earth, etc) that lies under another; substratum while underclay is (geology) a stratum of clay lying beneath a coal bed.

As a verb underlay

is (underlie) or underlay can be to lay (something) underneath something else; to put under.

In geology|lang=en terms the difference between stratum and underclay

is that stratum is (geology) a layer of sedimentary rock having approximately the same composition throughout while underclay is (geology) a stratum of clay lying beneath a coal bed.

As nouns the difference between stratum and underclay

is that stratum is one of several parallel horizontal layers of material arranged one on top of another while underclay is (geology) a stratum of clay lying beneath a coal bed.

As nouns the difference between underclay and thill

is that underclay is (geology) a stratum of clay lying beneath a coal bed while thill is one of the two long pieces of wood, extending before a vehicle, between which a horse is hitched; a shaft.