Describing the whole language with a comparatively small number of common words is the aim of most dictionaries, in particular the ones for young learners or foreign students. Some recent dictionaries have developed defining vocabularies, that is, lists of frequent words to be preferably used in definitions and explanations. Traditional dictionaries for native speakers often define easy words with more complex ones: for example, in the 1951 edition of the Concise Oxford Dictionary, arch was first described as: "curved structure supporting bridge, floor etc." Typical definitions of this kind begin with "the skill of...", "genus of plant...", "the act of...", "garment worn in...", "the part of the body..." Words like garment, skill, genus, act, structure play a central role and are qualified by means of appropriate adjectives and adverbials.

The Longman Dictionary of Contemporary English (that will be further described below) uses the Longman Defining Vocabulary (LDV) of around 2000 words. The list of the words beginning with a (third edition, 1995) follows:

a, ability, able, -able, about, above, abroad, absence, absent aj, accept, accident, accordance, according (to), account v n, accustom v, ache v n, acid, across, act v, action, active, activity, actor, actress, actual, add, addition, address v n, adjective, admiration, admire, admit, advance v n, advantage, adventure, adverb, advertise, advice, advise, affair(s), afford, afraid, after ad prep cj, afternoon, afterwards, again, against, age n, ago, agree, ahead, aim n v, air, -al, alcohol(ic), alike aj ad, alive, all aj ad, all right, allow, almost, alone, along, aloud, alphabet, already, also, although, altogether, always, among, amongst, amount, amuse, amusing aj, an, -an, -ance, ancient, and, anger n v, angle, angry, animal, ankle, annoy, another, answer n v, ant, anxiety, anxious, any, anybody, anyhow, anyone, anything, anywhere, apart, apparatus, appear, appearance, apple, appoint, approve, April, -ar, arch, archway, area, argue, arise, arm n v, armour n v, arms, army, around pr ad, arrange, arrangement(s), arrive, arrow, art, article, artist, as, ashamed, ash(es), at, -ate, -ation, atom(ic), attack n v, attempt n v, attend, attention, attentive, attract(ive), August, autumn, average n aj v, avoid, awake, away, awkward, axe n

If we compare these with the BASIC words beginning with <a>, we find a larger number of them (141 vs 44), which reflects the fact that LDV consists of about 2000 words (vs 850). In spite of this increase, we can see that adjustment, advertisement, agreement, amusement, approval, argument, attraction, authority and automatic are missing. All of these, except the last two, are de-verbal nouns deriving from verbs included in LDV: advertise, agree, amuse, approve, argue and attract; however adjust, from which adjustment derives, is missing.

A remarkable feature in the LDV list is the presence of the suffixes -able -al -an -ance -ar -ate -ation; elsewhere (that is, at their places in the alphabetical order), there are severl more affixes: suffixes like -ion and -ment; prefixes like im- in- ir- non- un- dis- for negative forms, re- for iterative forms, etc. The presence of such suffixes as -al -ion and -ment means that advertisement, agreement, amusement, approval, argument and attraction are to be considered as part of LDV, which therefore consists of well over 2000 items, although the extension is obtained through well-controlled affixation processes.

An important remark by the chief editor(10) of the dictionary, Lord Quirk, is that

Without this, the selection of a defining vocabulary would be totally useless. In the end, however, the only criterion that is offered to justify the choices is the experience that the publishing house has acquired through the production and diffusion of a large number of different materials for the teaching of English as a foreign or second language.