Humpty Dumpty, as Alice discovered in Through the Looking Glass, had his own personal vocabulary. "When I use a word," he said, "it means just what I choose it to mean - neither more nor less."
For some time, the Government has been accused of employing a similarly lopsided lexicon to fit its own image of education in England. This week a row broke out over ministers' employment of one word in particular - aptitude - to justify one of its most controversial policies: the continuing use of selection in hundreds of state schools.
The fall-out centres upon its 2,602 specialist schools, and a handful of new-style academies, which are granted powers to pick a proportion of pupils based on their aptitude, or "potential", for a particular subject.
Ministers say that, while selecting children by ability is discriminatory, those who display an aptitude for subjects, such as languages or sport, should be able to shine. Critics, on the other hand, claim that the distinction is a myth, peddled by ministers to justify the seemingly unstoppable rise of specialist schools. So is the Government's distinction between the two words fact or fiction?
Professor Alan Smithers, from the Centre for Education and Employment Research, at Buckingham university, is under little doubt. "You can draw parallels between the fictional character, who said 'words are what I say they mean', and the Government's definitions of aptitude and ability," he said. "This is an area of considerable embarrassment to the Government because many backbenchers are opposed to selection by ability.
Nevertheless, to give some credence to the impression that its specialist schools are real subject specialists, the Government has given them powers to select on talent. It came up with this purely political distinction between ability and aptitude, which really has no meaning in reality. It is a grey area to say the least."
The origins of the row date back to the Conservative government, which introduced specialist technology colleges in 1994 to improve standards of design and technology and ICT. Powers were devolved to the schools, set up as centres of excellence, to select 10 per cent of local pupils who displayed a particular aptitude for the subjects. Under New Labour, the specialist college programme flourished and schools were soon able to specialise in a number of new areas, including the arts, humanities, languages and sport. But as the policy gathered strength, so did calls, led by the Labour left, to scrap selection.
As early as 1996, a study by the National Foundation for Educational Research had suggested tests used by technology colleges to measure aptitude were unreliable, and under New Labour, criticism of the process has failed to wane.
In 2003, the Office of the Schools Adjudicator raised its own concerns after reprimanding 10 schools in Hertfordshire for apparently using the powers to select the brightest pupils - not those with the most potential.
Philip Hunter, the chief adjudicator, said: "One of the difficulties is the law uses these two words as if they were separate things and actually they are not."
A year later, a cross-party group of MPs on the House of Commons education select committee went further by calling for the powers, which are exercised by some 6 per cent of specialist schools (around 160) and half the 27 academies, to be scrapped. The MPs based their decision, in part, on evidence from Mr Hunter who said that defining the difference between aptitude and attainment was "the sort of exercise lexicographers get up to when they haven't enough to do".
In response, ministers agreed to a reform of the laws, effectively reducing the number of schools able to exercise the right to select. It said that from September 2007 secondary schools can only select if they have specialist status in modern languages, music, performing arts, visual arts or sport. No specialist design and technology or ICT schools will be able to use these powers, they said, unless they already do so.
In more recent times, the Government has attempted to iron out the difficulties further, by offering its own definition of aptitude in its new draft code of practice for school admissions (see box, right).
But unease surrounding the use of the word persists. This month, the adjudicator's office exposed further, persistent, flaws in the system by criticising one of England's first technology colleges, George Spencer foundation school, on the outskirts of Nottingham. Following a complaint from the local council, it said George Spencer had been selecting pupils by ability - not aptitude - for years.
Sir Cyril Taylor, a Downing Street education adviser and architect of the specialist schools programme, envisages that every secondary in England will be specialist in a few years' time.
This little row may rumble on for some time...
The official admissions body criticised George Spencer foundation school for selecting a proportion of pupils on their prior attainment - not future potential.
Alan Parker, the adjudicator, said the school sent an A4 form to local primary heads, which contained a list of 20 questions to gauge a child's aptitude for technology. One question asked what level of skill a child had for using spreadsheets, and heads were told to rank performance on a scale of one to five.
Chris Whetton, an academic from the National Foundation for Educational Research, said the test had nothing to do with "aptitude". He said: "The measures are of prior attainment and not of aptitude, since those students who have not had the opportunity to follow a particular course of study would not have the means to demonstrate aptitude."
Mr Parker added: "It is not hard to see that a simple tick-box exercise, lacking in detailed instructions ... would be unlikely to yield reliable and consistent results."
APTITUDE VERSUS ABILITY
The Oxford English dictionary is not much help when it comes to differentiating between aptitude and ability - not least because one definition of "aptitude" is "natural ability".
According to the Chambers English dictionary, the two are similarly hard to distinguish. Aptitude is said to be "fitness", "tendency to", "natural ability" and "readiness to learn". Ability, meanwhile, is "being able to", "power (physical and mental)", "strength" and "skill".
The Government offers its own definition in the recently-published draft code of conduct on school admissions. "A pupil with aptitude is one who is identified as being able to benefit from teaching in a specific subject, or who demonstrates a particular capacity to succeed in that subject," it says. "The essential factor that the admission authority must determine is whether a child demonstrates a particular capacity to learn or to develop skills in that subject, and that he or she can benefit from the particular expertise and facilities at that school."