3rd declension

Consonant stems - imparisyllaba, one syllable more in gen then in nom sg. (and other cases as well)   ( stem = gen sing - is)     gen pl. m.f.n.   -UM

m.  and   f.     (the same declension)

 typical endings :      m.  victor, -oris     mos, moris     leo, leonis               passer, passeris     iudex, iudicis   

 f.   virgo, virginis     virtus, virtutis,    fortitudo, fortitudinis    lex, legis, natio, nationis      pax, pacis     civitas, civitatis,    palus, paludis

neuter

  neuter:    corpus, corporis, n.     caput, capitis n.  guttur, gutturis, n.

     robur, roboris n.     tempus, temporis, n.     genus, generis n.                  

      lac, lactis n.     mel, mellis n

    
Vocal stems       -         gen pl  - ium

 1. parisyllaba    (the same amount of syllables in nom and gen. sing)

navis, navis,  f.        civis, civis  c. (= m&f.)   canis, canis  c. (m.f.)

   clades, cladis, f.   

2. with consonant group in gen. sg (before -is)    (parisyllaba and imparisyllaba)    

mons, montis,  m.      pars, partis  f.     imber, imbris m.

     ars, artis f.

3. neuter ending in -e   -al    - ar         abl sg  - i        pl.  nom/acc  - ia         gen pl   - ium    

  animal, animalis, n.        calcar, calcaris, n. 

N.B. there are exceptions in gender, but typical endings help a lot to recognise other similar nouns                              -  and exceptions in gen pl (i.e. parens, parentis m/f   gen pl parentum and parentium,    pater, patris m   gen. pl