a. Et, and, simply connects words or clauses; -que combines more closely into one connected whole. -que is always enclitic to the word connected or to the first or second of two or more words connected:
b. Atque (ac), and, adds with some emphasis or with some implied reflection on the word added. Hence it is often equivalent to and so, and yet, and besides, and then. But these distinctions depend very much upon the feeling of the speaker, and are often untranslatable: -
c. Atque (ac), in the sense of as, than, is also used after words of comparison and likeness: -
For and not, see §328. a.
d. Sed and the more emphatic verum or vero, but, are used to introduce something in opposition to what precedes, especially after negatives (not this . . . but something else). At (old form ast) introduces with emphasis a new point in an argument, but is also used like the others; sometimes it means at least. At enim is almost always used to introduce a supposed objection which is presently to be overthrown. At is more rarely used alone in this sense.
Autem, however, now, is the weakest of the adversatives, and often marks a mere transition and has hardly any adversative force perceptible. Atque, however, now, sometimes introduces all objection and sometimes a fresh step in the reasoning. Quod si, but if, and if, now if, is used to continue an argument.
NOTE: Et, -que, and atque (ac) are sometimes used where the English idiom would suggest but, especially when a negative clause is followed by an affirmative clause continuing the same thought: as, - impetum hostes ferre uon potuerunt ac terga verterunt (B. G. iv. 35), the enemy could not stand the onset, but turned their backs.
e. Aut, or, excludes the alternative; vel (an old imperative of volo) and -ve give a choice between two alternatives. But this distinction is not always observed: -
f. Sive (seu) is properly used in disjunctive conditions (if either . . . or if), but also with alternative words and clauses, especially with two names for the same thing: -
g. Vel, even, for instance, is often used as an intensive particle with no alternative force: as, - vel minimus, the very least.
h. Nam and namque, for, usually introduce a real reason, formally expressed, for a previous statement; enim (always postpositive), a less important explanatory circumstance put in by the way; etenim (for, you see; for, you know; for, mind you) and its negative neque enim introduce something self-evident or needing no proof.
i. Ergo, therefore, is used of things proved formally, but often has a weakened force. Igitur, then, accordingly, is weaker than ergo and is used in passing from one stage of an argument to another. Itaque, therefore, accordingly, and so, is used in proofs or inferences from the nature of things rather than in formal logical proof. All of these are often used merely to resume a train of thought broken by a digression or parenthesis. Idcirco, for this reason, on this account, is regularly followed (or preceded) by a correlative (as, quia, quod, si, ut, ne), and refers to the special point introduced by the correlative.
j. Autem, enim, and vero are postpositive[That is, they do not stand first in their clause.] ; so generally igitur and often tamen.
k. Two conjunctions of similar meaning are often used together for the sake of emphasis or to bind a sentence more closely to what precedes: as, at vero, but in truth, but surely, still, however;
For Conjunctions introducing Subordinate Clauses, see Syntax.