Allen and Greenough's New Latin Grammar for Schools and Colleges
J. B. Greenough, G. L. Kittredge, A. A. Howard, Benj. L. D'Ooge, Ed.

1. “proptereā quod aliud iter habērent nūllum ” (B. G. 1.7) , because (as they said) they had no other way.
2. “ ūnī epistulae respondī, veniō ad alteram ” (Fam. 2.17.6) , one letter I have answered, I come to the other.
3. “ alterum genus ” (Cat. 2.19) , the second class.
4. “iēcissem ipse mē potius in profundum ut cēterōs cōnservārem ” (Sest. 45) , I should have rather thrown myself into the deep to save the rest.
5. “Servīlius cōnsul, reliquīque magistrātūs ” (B. C. 3.21) , Servilius the consul and the rest of the magistrates.
6. “cum sit necesse alterum utrum vincere ” (Fam. 6.3) , since it must be that one of the two should prevail.

[*] Note.-- Alter is often used, especially with negatives, in reference to an indefinite number where one is opposed to all the rest taken singly:—

1. “dum nē sit tē dītior alter ” (Hor. S. 1.1.40) , so long as another is not richer than you (lit. the other, there being at the moment only two persons considered).
2. nōn ut magis alter, amīcus (id. 1.5.33), a friend such that no other is more so.

[*] a. The expressions alter ... alter, the one ... the other, alius ... alius, one ... another, may be used in pairs to denote either division of a group or reciprocity of action:—

1. “ alterī dīmicant, alterī victōrem timent ” (Fam. 6.3) , one party fights, the other fears the victor.
2. “ alteram alterī praesidiō esse iusserat ” (B. C. 3.89) , he had ordered each (of the two legions) to support the other.
3. “ aliī gladiīs adoriuntur, aliī fragmentīs saeptōrum ” (Sest. 79) , some make an attack with swords, others with fragments of the railings.
4. “ alius ex aliō causam quaerit ” (B. G. 6.37) , they ask each other the reason.
5. “ alius alium percontāmur ” (Pl. Stich. 370) , we keep asking each other.

[*] b. Alius and alter are often used to express one as well as another (the other) of the objects referred to:—

1. alter cōnsulum, one of the [two] consuls.
2. “ aliud est maledīcere, aliud accūsāre ” (Cael. 6) , it is one thing to slander, another to accuse.

[*] c. Alius repeated in another case, or with an adverb from the same stem, expresses briefly a double statement:—

1. alius aliud petit, one man seeks one thing, another another (another seeks another thing).
2. “iussit aliōs alibī fodere ” (Liv. 44.33) , he ordered different persons to dig in different places.
3. “ aliī aliō locō resistēbant ” (B. C. 2.39) , some halted in one place, some in another.