1. What do the following words have in common?

COW
VIXEN
DAMSEL

2. What do the following words have in common?

NOVEL
JUNIOR
SEPTIC
APRON
DECLARE

HINTS:
1. It has to do with numbers.
2. It has to do with a group of twelve.


Answers:

1. Between them, they contain all seven Roman Numerals (I, V, X, L, C, D, M)

2. The first three (or four) letters of each word are abbreviations for months of the year.

(Credit: Chicago Tribune Crossword
Josiah Breward - ABBREVIATED CALENDAR)