Latin diminutive

The Latin language has a robust diminutive-forming system. There are many diminutive suffixes: those in calculus, axilla, fistula, and areola to start. There is often more than one correct way to form a diminutive, and many more incorrect ones.

Gender
The masculine, feminine, and neuter diminutives often end in -us, -a, and -um.
 * later, -is (m.) > later-cul-us (m.)
 * mulier, -is (f.) > mulier-cul-a (f.)
 * tūber, -is (n.) > tūber-cul-um (n.)

There are exceptions. These masculine words end in -a:
 * scurr-a (m.) > scurr-ul-a (m.)
 * vern-a (m.) > vern-ul-a (m.)

Many have a vowel, followed by one or two ls, followed by the endings just mentioned. Here we see stem + 'ul' + ending.

The rules can be a bit involved. The diminutive depends on the gender, declination (first, second, etc.) and the root's ending.

Regula Generalis
In general the diminutive of nouns of the first or second declension which end in obstruents or the semivowel /w/ (written ) take the suffix -ulus/-ula/-ulum (depending on gramatical gender).

Stems ending in Vowels
Nouns of the first or second declension whose stems end in a vowel typically take -ola, -olus, or -olum depending on if they are of the feminine, masculine, or neuter gender respectively. Words ending in the glide /w/ (written v), take -ul- like other stems ending in consonants (cf. cerva/cervula).

In the first declanation, -ia can become =illa or =ola. (Lucia → Lucilla, sed Tullia → Tulliola).

Roots with -ul-
Nouns whose stems end in -ul- (either the root itself, or due to the noun in question being a diminutive already), when their diminutive is formed, the stem-final, -ul- changes either to -ell- or -ill-. It is difficult to find any regular correspondence between the context surrounding -ul- and whether the diminutive's stem ends in -ell- or -ill-.

In the table below, those which are diminutives already have the original stem listed under "principle". In cases where the diminutive's meaning is very different from that of the original noun, the noun in question is enclosed with parentheses.

The double diminutives of words ending in -er, or -in-, are usually formed by adding -ul- to the end of the existing diminutive..

Third declension
in -es, -is & -e

More nouns, third declination

Fifth declination
In the fifth declension, Latin nouns generally take -cula.