With names of Towns and Islands small enough to be considered one place, the prepositions to, from or at are expressed simply by (respectively) the accusative, ablative and locative cases; prepositions must, however, be used with (a) all proper names, (b) all common names, and (c) when the neighbourhood of a town is meant.

Ab becomes á- before m and v; abs- before c and t; and as- before p.

Ad becomes ac- before c and q (and sometimes before other consonants); and sometimes a- before sc, sp and st; ar- is found in arcessere and arbiter.

Ambi- becomes amb- before vowels; am- before p; and an- before c and q.

Ante becomes anti- in antistáre.

Circum sometimes drops m: e.g., circuíre.

Contrá sometimes becomes contró-.

Cum generally becomes con-; but com- before b, m and p; col- before l; cor- before r; có- before n; and co- before vowels and h.

Dis- becomes dif- before f; di- before d, g, l, m, s and v when they are followed by another consonant; and dir- before vowels.

Ex becomes ef- and sometimes ec- before f; but remains ex- before vowels, h, c, p, s and t; and e- elsewhere. s following x is sometimes dropped, as in expectare.

In becomes im- before b, m and p; and sometimes becomes il- before l and ir- before r.

Inter is assimilated only in intel-legere.

Intrá becomes intró-.

Ob becomes oc- before c, of- before f, op- before p; and sometimes written (as pronounced) op- before s and t.

Per becomes pel- only in pel-licere and pel-lúcére. Compounded with adjectives, Per often means very. [The per- in perfidius and perjúráre surely must mean something like beyond---note tha parallel use of for- in forswear. There will be a link to a longer note on these words, later.]

Por- becomes pol- before l; and pos- before s.

re- before consonants except reddere; and red- before vowels: note Repperí, Reppulí and Rettulí.

sé- before consonants; and sed- before vowels.

Sub usually becomes sus- before s, sus- before s, suc- before c, suf- before f, sug- before g, sum- before m and sur- before r---but note subruere; Sub sometimes becomes sus- before c, p and t: sus- is found in the phrase, susque déque---above and below, of no consequence. In composition with adjectives Sub often means slightly.

Tráns becomes trá- before d, j---thus traicere (since i = ji)---and before n; and sometimes before l and m.

With denoting the Instrument is expressed by the simple Ablative. With meaning together with, denoting accompaniment, is expressed by cum with the Ablative. With denoting the Manner, is expressed by the Ablative if an epithet be added, otherwise by cum with the Ablative.

Tenus always follows its case. Fíne is sometimes used similarly: e.g., fíne genús--as far as the knee.

Versus usually follows its case.

Super is often used with the Accusative where no motion is intended, and rarely in the Ablative.