AIR - The atmospheric substance above the surface of the earth which animals breathe, formerly considered to be a single substance, one of the four basic elements of ancient philosophy and one of the five basic elements of Eastern traditions.
RAT - A medium-sized rodent belonging to the genus Rattus.
TAR - A black, oily, sticky, viscous substance, consisting mainly of hydrocarbons derived from organic materials such as wood, peat, or coal.
VIA - A main road or highway, especially in ancient Rome. (Mainly used in set phrases, below.).
VAT - A large tub, such as is used for making wine or for tanning.
AIL - Painful; troublesome.
ALT - A state of excitement, conveyed by a high pitched voice.
LAT - A Latvian coin and national monetary unit.
LIAR - One who tells lies.
RAIL - A horizontal bar extending between supports and used for support or as a barrier; a railing.
TAIL - The caudal appendage of an animal that is attached to its posterior and near the anus.
VIAL - A glass vessel or bottle, especially a small bottle used to store medicine or perfume.
LAIR - A place inhabited by a wild animal, often a cave or a hole in the ground.
RIVAL - A competitor (person, team, company, etc.) who is well known to another and has similar skills and achievements. Defeating a rival may be a primary or necessary goal of a competitor.
TRAIL - To follow behind (someone or something); to tail (someone or something).
TRIAL - An opportunity to test something out; a test.
VIRAL - Of or relating to a biological virus.
VITAL - Relating to, or characteristic of life.
TRIVIA - Insignificant trifles of little importance, especially items of unimportant information.
TRIVIAL - Of little significance or value.