One Word Substitution

Aristocracy is a form of government where power is held by the noble or privileged class. The term combines Greek 'aristos' (best) + 'kratos' (rule). Historically, aristocracies were ruled by hereditary nobility believed to be the 'best' suited to govern due to birth, wealth, or social standing.

A valetudinarian is someone who constantly obsesses about their health and thinks they are always ill. The word derives from Latin 'valetudo' (health, state of being sick). These individuals exhibit excessive health anxiety, often complaining about minor ailments and displaying hypochondriac tendencies.

Gullible describes someone who is easily deceived, tricked, or persuaded. The word comes from 'gull' (to deceive or cheat). Gullible people tend to believe things too readily, accept statements without verification, and are vulnerable to scams, tricks, or manipulative tactics due to their trusting nature.

An atheist denies the existence of God; an agnostic questions the existence of God i.e. doubts the existence...does not reject the existence of God.

Colleagues are people who work together in a professional setting. The other options refer to different concepts - predator (one who preys on others), bigot (intolerant person), parasite (one who benefits at another's expense).

Somniloquist refers to someone who talks in their sleep. This is derived from Latin 'somnus' (sleep) and 'loqui' (to speak).

An epicure is someone who appreciates and cultivates refined sensuous pleasures, especially good food and drink. The term comes from the Greek philosopher Epicurus.

Equilibrium describes a state of perfect balance between opposing forces or influences. In physics, it means all forces are balanced; in chemistry, it's when reactions stabilize.

Illegible handwriting or text is impossible or very difficult to read. The prefix 'il-' means not, and 'legible' means able to be read.

Physiology is the scientific study of how the human body and its various parts function. Botany studies plants, ornithology studies birds.

An anonymous work is one where the author's identity is unknown or not revealed. The term comes from Greek 'anonymos' meaning 'without name'.

Polygamy specifically means having multiple spouses. The prefix 'poly-' means many, and 'gamy' refers to marriage.

Deterioration means to become worse or lower in quality. Other options are incorrect.

Anatomy is the science dealing with the structure of animals and plants. 

A 'yuppie' refers to a young, well-educated, urban professional who earns a good salary and holds a prestigious job. The term originated in the 1980s and stands for 'young urban professional' or 'young upwardly-mobile professional'. Brigade means an army unit, bourgeois refers to middle class, and maverick means an independent thinker.