Latin often leaves out a word the reader can supply, especially est, sunt and esse, or a verb already used in the same sentence.
Forms of sum are left out most often. A nominative with an adjective, noun or participle and no verb needs "is" or "are": natura, fluxa "its substance (is) in flux". A participle or gerundive alone may stand for a whole verb: veneranda for veneranda sunt, nec deinceps rediturum for nec deinceps rediturum est "and it will not come back".
In infinitives, esse is often dropped: praescriptum for praescriptum esse, moriturum for moriturum esse.
A verb used once can serve a second clause too: in quae enim Dii agunt, … quae homines, … sunt amica, supply agunt again, "what men (do)". In comparisons, look for the missing verb in the first half.
A verb of saying may be left out before a quotation or a command: tu ergo sic tecum "so (say) to yourself".