AFFECT is a verb, meaning to have an influence on as in Smoking affects the heart. (It has another, less common meaning, to assume or to pretend, as in she affected to believe that she could hand in her essay whenever she liked.)
AFFECT should not be confused with EFFECT, which as a verb means to bring about as in Houdini effected his escape. Confusion stems from its principal meaning as a noun an effect means a result or a consequence: his belief that spelling did not matter had the effect of annoying employers.
BARREN means bare and should not be confused with BARON, a lord.
BORN refers to birth. BORNE means carried.
CIVILISATION, CIVILIZATION Both spellings are correct, but the Z form is more common.
COMPLEMENT and COMPLIMENT If I say something flattering about your work, it is a COMPLIMENT. If extra evidence endorses the conclusion of your essay, it COMPLEMENTS your argument.
CURRANT and CURRENT A currant is a small fruit, e.g. a blackcurrant. A current is a moving force, of air, water or electricity (as in electric current). As an adjective, current means now or continuing (as in current events).
DEFUSE and DIFFUSE The verb to defuse was coined during the Second World War to describe the act of disabling a bomb. It is gradually crowding out the similar verb to diffuse, meaning to scatter or dispel. He defused the tension by telling a joke. He diffused the tension by telling a joke. In the first example, tension is a bomb about to explode. In the second, it is a poisonous element which needs to be blown away.
DISCREET and DISCRETE A DISCREET person is judicious, circumspect and tactful, somebody who can be trusted with confidential information. It is an adjective exclusively applied to people. DISCRETE, meaning separate or distinct, invariably describes things, as in a discrete problem or a discrete entity.
ECONOMIC is an adjective generally relating to ECONOMY and ECONOMICS. R.H. Tawney was an economic historian. The government failed in its economic policy.
ECONOMICAL means careful with money or resources. She was economical in spending her student loan. He was economical with the truth.
EFFECT See AFFECT
ENSURE means to make an outcome certain as in he worked hard to ensure that he passed the exam. This should not be confused with INSURE, to arrange to receive compensation in the event of accident or illness, as in she should insure her house against fire.
HISTORIC and HISTORICAL Any episode that took place in the past is a HISTORICAL event (so long as we have evidence to reconstruct what happened). Only these events that were landmarks, turning points or productive of important consequences should be called HISTORIC. The term historic is devalued when used to describe football matches.
HOARD means to collect and store things without intending to use them in the near future. It should not be confused with HORDE, meaning a large and frightening array of people or animals.
INSURE See ENSURE
JUDGEMENT, JUDGMENT Both spellings are correct, although the first is probably more common.
LAY and LIE
These two verbs are often confused in ordinary speech.
LAY is always transitive and means to place somebody or something [usually on a lower level]. The present tense is lay/lays. The perfect tense is laid, and the past participle is also laid.
The chicken lays an egg.
Yesterday, the chicken laid an egg.
When we came home, we found that the chicken had laid an egg.
LIE, meaning to locate oneself in a horizontal position, is always intransitive. The present tense is lie/lies, the past tense is lay, and the past participle is lain.
He lies on the ground.
When he returned from the library, he lay on the couch.
He had lain on the couch for some time when the telephone rang.
Most people regard lain as old‑fashioned, and nowadays we should normally say he had been lying on the couch. However, laid should never be used as any form of past tense for lie.
When LIE means to tell a falsehood, the past tense is lied.
LEAD/ LEAD/ LED (to rhyme with breed, bread, bred). There is no serious problem about lead (rhyming with breed): as a verb to go on ahead and show the way; as a noun a leather rope to control an animal.
The past tense of the verb to lead is led L‑E‑D.
Obviously this is inconsistent with the past tense of the verb to read (rhyming with breed), which is read (rhyming with bred).
However, the inconsistency can be explained by comparing:
Yesterday, I read a book and Yesterday, I lost a book with a red cover
I have led a wicked life and There is too much lead in petrol.
LED see LEAD
LICENCE is a noun, referring (for instance) to a piece of paper which proves that a person has passed a driving test. LICENSE is the verb.
There are various memory tricks for remembering the distinction between them: a licence is a piece of paper, to license is a process. Licence is a noun, license is a verb; in the alphabet, C comes before S, N comes before V.
Another way of distinguishing between them is by association with advice (noun) and advise (verb).
The same distinction applies to practice (noun) and practise (verb).
By some bizarre process, LICENSE as a noun means anarchy, diametrically opposite to the process of control implied by the verb. If there were no traffic regulations, there would be complete license on the roads.
LIE See LAY
LOOSE, which rhymes with juice, should not be confused with LOSE (which rhymes with ooze) but has only one O.
MARSHAL is a verb meaning to organise people into military order or to organise arguments in a logical manner. As a noun it refers to an officer or official responsible for organising people.
MARTIAL is an adjective generally related to fighting, as in martial arts or martial music.
METER / METRE A meter is a measuring machine. For basic commodities, it forms part of two-word phrases, such as electricity meter and water meter. However, in most instances, it forms part of a compound word: hydrometer, speedometer. A gas meter measures how much gas flows into your home, but a gasometer is the giant container that holds the supply.
A metre is a unit of measurement, approximately equal to 39.37 inches. It was invented following an inaccurate attempt in the 1790s to measure the circumference of the earth, and remains one of the more irritating legacies of the French Revolution. (Napoleon, to his credit, tried to abolish it.) It forms various compounds, such a centimetre and kilometre.
Confusingly, metre has an additional meaning, referring to the rhythm of poetry. By extension this can also apply to the beat of music. Hence the adjective metric refers to a measuring system, but metrical describes a form of music. In strict logic, a device for measuring rhythm should be called a metremeter, but this absurdity is avoided by the term metronome.
American English sweeps all this aside by using er forms in all cases. However, the United States does not officially recognise the metric system.
MORAL / MORALE The moral of the story was obvious.
Bureaucrats destroyed the morale of university staff.
POPULACE is a pompous word for people and should not be confused with POPULOUS, an adjective referring to areas or countries which have large populations.
PRACTICE is a noun and PRACTISE is a verb. In practice, you have to practise to get this right. See also LICENCE and LICENSE.
PRINCIPAL may be used either as a noun or as an adjective. It means chief.
The Principal of the University was not my pal.
Poor spelling was the principal reason why she did not get the job.
PRINCIPLE is a noun, meaning noble or inspiring belief. It should never be used as an adjective.
REIGN is a noun or verb which refers to the span of time in which a monarch occupies the throne: the reiGn of George V.
REIN may also be used as noun or verb, and refers to methods of controlling an animal.
SIGHT, SITE and CITE are words with very different meanings.
Icebergs are sighted off Newfoundland even in August.
Vancouver is sited on the west coast of Canada.
Sources of quotations must be cited in footnotes.
STATIONARY means immobile as in a parked car. STATIONERY is writing paper for letters.
THEIR and THERE There is no place in a university for students who show their ignorance of the difference between these two words.
YOKE and YOLK A yoke is a wooden frame fitted to draught animals to harness them. By extension, it came to refer to any humiliating burden, as in the Norman yoke.
In colloquial usage in Ireland, yoke is used to mean thing, as in Put that yoke away.
The yellow part of an egg is the yolk.