Introduction
Second Declension Nouns
Includes masculine and neuter nouns.
Masculine nouns typically end in -us in the nominative singular and -i in the genitive singular.
Neuter nouns typically end in -um or -on in the nominative singular.
The most distinctive feature of neuter nouns is that the nominative singular and accusative singular forms are always the same, and the nominative plural and accusative plural forms are always the same.
Important to memorize the gender of all second declension nouns to help with understanding Latin's declensions.
Second Declension Adjectives
Agree with the nouns they modify in gender, number, and case.
Masculine adjectives end in -us or -er in the nominative singular.
Neuter adjectives end in -um in the nominative singular.
Exceptions and Special Cases
Some masculine nouns end in -er in the nominative singular, and for these nouns, only the -e- is dropped in the declension forms.
Some Greek nouns of the feminine gender belong to the Second Declension.
While the First Declension is typically associated with feminine nouns and the Second Declension is typically associated with masculine and neuter nouns, there are exceptions, making it crucial to memorize the dictionary form of nouns.
Examples
Masculine Nouns: nervus (nerve), cancer (cancer), locus (place)
Feminine Nouns: diameter (diameter), methodus (method), periodus (period)
Neuter Nouns: cranium (skull), colon (colon), ganglion (ganglion), acromion (continuation of the scapular spine), olecranon (large, curved bony eminence of the forearm that projects behind the elbow)
Masculine Adjectives: acutus (acute), dexter (right), malignus (malignant)
Neuter Adjectives: dextrum (right), congenitum (inborn), malignum (malignant), benignum (benign), exquisitum (acquired), chronicum (chronic), sinistrum (left)
Additional Information
Expressions with Ablative: in loco + Genitive (in the place of), in loco typico (in a typical place), in vivo (in a living organism), in vitro (in an artificial medium), with/without attached (uterine appendages)
Neuter nouns of the Second Declension include: the names of chemical elements (argentum - silver, aurum - gold) and many trademarks of medicines (codeinum - codeine, glycerinum - glycerin)
Words with similar sounds but different meanings: collum (neck) & colon (colon), ileum (ileum) & ileus (intestinal obstruction)