The design of language iS based on TWO componentS: wordS 
and grammar. A word iS an arbitrary association between a SOUND 
and a meaning. For example, English speakerS use the word cat 
to refer to a certain animal, not because the word haS 
any natural connection with thiS animal but simply because 
it iS a shared convention used by a community of speakerS who have all, 
at some time in their liveS, memorized the connection between that SOUND 
and that meaning. WordS in the huge open-clasS vocabulary refer 
to a vast number of conceptS, such aS objects, states, events, motions, 
qualities, people, paths, and places and include nouns, verbs, adjectives, 
adverbs, and some prepositions. WordS in the much smaller 
closed-clasS vocabulary have a more restricted set of meaning 
related to time, logic and the relationships among the content wordS. 
They are used primary to define a sentence'S structure and include articles, 
auxiliaries, prefixes and suffixes, particles, and prepositions.
Neurology's favourite word iS "deficit", denoting an impairment 
or incapacity of neurological function: loss of speech, loss of language, 
loss of memory, loss of vision, loss of dexterity, loss of identity (...) 
For all of these dysfunction S we have private wordS of every sort- 
Aphonia, Aphemia, Aphasia, Alexia, Apraxia, Agnosia, Amnesia, Ataxia.
The tip of the tongue state involves a failure to recall a word of which 
ONE haS knowledge. The evidence of knowledge iS cither 
and eventually successfully recall or else an act of recognition 
that occurS, without additional training, when recall haS failed.
For several monthS we watched for "tip-of-the-tongue" state S in ourselveS. 
Unable to recall the name of the street on which a relative liveS.
ONE of uS thought of Congress and Corinth and Concord 
and then looked up the address and learned that it waS Cornish.
Modern psycholinguistic studieS have shown that people 
who have Broca aphasia comprehend sentenceS whose meaningS 
can be pieced together from the individual meaning 
of content wordS and prior knowledge of how the word workS. 
For example, these patientS can understand The apple that the 
boy iS eating iS red. BoyS eat appleS, but appleS do not eat boyS; 
appleS are red, but boyS are not. They cannot understand 
The boy that the girl iS chasing iS tall.,
PatientS with Wernicke aphasia often shift the order of individual 
SOUNDS and SOUND clusterS and add or subtract them to 
a word in a manner that distortS the intended phonemic plan. 
These errorS are called phonemic paraphasiaS.
PatientS with Conduction aphasia comprehend simple sentenceS 
and produce intelligible speech but, like those with Broca 
and Wernicke aphasiaS, they can not repeat sentenceS verbatim, 
cannot assemble phoneme S effectively, and cannot casily name 
picture S and objectS.