ARE - Second-person singular simple present tense of be.
ART - Human effort to imitate, supplement, alter, or counteract the work of nature.
ATE - Simple past of eat.
EAR - The organ of hearing, consisting of the pinna, auditory canal, eardrum, malleus, incus, stapes and cochlea.
ERA - A time period of indeterminate length, generally more than one year.
TAR - A black, oily, sticky, viscous substance, consisting mainly of hydrocarbons derived from organic materials such as wood, peat, or coal.
TEA - The dried leaves or buds of the tea plant, Camellia sinensis.
TEE - The name of the Latin script letter T/t.
ERR - To make a mistake.
RARE - Cooked very lightly, so the meat is still red (in the case of steak or beef in the general sense).
RATE - A wage calculated in relation to a unit of time.
REAR - To raise physically; to lift up; to cause to rise, to elevate.
TART - Sharp to the taste; acid; sour.
TEAR - To rend (a solid material) by holding or restraining in two places and pulling apart, whether intentionally or not; to destroy or separate.
TREE - A large plant, not exactly defined, but typically over four meters in height, a single trunk which grows in girth with age and branches (which also grow in circumference with age).
EATER - Agent noun of eat; one who eats.
RATER - One who provides a rating or assessment.
TREAT - An entertainment, outing, or other indulgence provided by someone for the enjoyment of others.
TERRA - A rough upland or mountainous region of the moon with a relatively high albedo.
RETREAT - The act of pulling back or withdrawing, as from something dangerous, or unpleasant.