means "long" than heightened means "high" or strengthened means "strong." It is correct to say "He lengthened the discourse, but it was still too short"; but not to say "He quoted a lengthened passage from the sermon." In the latter illustration lengthy should be used. A sermon is lengthy when "unusually or unduly long" (with a suggestion of tediousness), not when it is simply "long."
lengthways, sideways, endways: Common but none the less undesirable variants of lengthwise, sidewise, endwise.
less. Compare few.
lessen. Compare reduce.
let her rip: Farmer, in his "Americanisms Old and New," says, this "most vulgar of vulgarisms" is used to convey the idea of intensity of action. The phrase is coarse and should not be used as a substitute for "go ahead."
level, on the: A vulgar intensive used to emphasize the fact that the thing stated is stated truthfully, or that the person spoken of is, to the speaker's knowledge, upright and "on the square." Compare square.
levy, levee: Exercise care in the use of these words. Levy is to impose and collect by force; levee, a morning reception.
liable, likely: The first of these words which is properly used as expressive of "having a tendency"