Masculine Nouns usually end with consonant or Й.
Feminine Nouns normally end with -А or -Я.
Neuter Nouns most often end with -О or -Е.
There are exceptions. For instance, ПАПА (father) is
a masculine noun. Also most nouns ending -Ь are feminine such as
МАТЬ and ДВЕРЬ, but
some ending -Ь are masculine such as ДЕНЬ or
ДОЖДЬ. Also nouns such as
ВРЕМЯ and ИМЯ that end
-МЯ are neuter.
(the boy walked home)
(the cat slept under the table)
(he reads the newspaper every morning)
(the window is open)
(the door is closed)