free

In obsolete terms the difference between plain and free

is that plain is a plane while free is freely; willingly.

As adjectives the difference between plain and free

is that plain is flat, level while free is unconstrained.

As adverbs the difference between plain and free

is that plain is simply while free is without needing to pay.

As nouns the difference between plain and free

is that plain is a lamentation while free is abbreviation of free kick.

As verbs the difference between plain and free

is that plain is to lament, bewail while free is to make free; set at liberty; release; rid of that which confines, limits, embarrasses, or oppresses.

Splendid is a related term of free.

As adjectives the difference between splendid and free

is that splendid is possessing or displaying splendor; shining; very bright; as, a splendid sun while free is (label) unconstrained.

As an adverb free is

without needing to pay.

As a verb free is

to make free; set at liberty; release; rid of that which confines, limits, embarrasses, or oppresses.

As a noun free is

(australian rules football|gaelic football) abbreviation of free kick.