Prescription and description in conflict
Given any particular language controversy, prescription and description represent quite different, though not necessarily incompatible, approaches to thinking about it.

For example, a descriptive linguist working in English would describe the word ain't in terms of usage, distribution, and history, observing both the growth in its popularity but also the resistance to it in some parts of the language community. Prescription, on the other hand, would consider whether it met criteria of rationality, historical grammatical usage, or conformity to a contemporary standard dialect. When a form does not conform — as is the case for ain't — the prescriptivist will recommend avoiding it in formal contexts. These two approaches are not incompatible, as they attempt different tasks for different purposes.

However, description and prescription can appear to be in conflict when stronger statements are made on either side. When an extreme prescriptivist wishes to condemn a very commonly used language phenomenon as solecism or barbarism or simply as vulgar, the evidence of description may testify to the acceptability of the form. This would be the case if someone wished to argue that ain't should not even be used in colloquial spoken English. Prescriptive statements will sometimes be heard which suggest that a word is inherently ugly; a descriptive approach will deny the meaningfulness of this judgment. In such instances of controversy, most linguists fall heavily on the descriptive side of the argument, accepting forms as correct or acceptable when they achieve general currency.

On the other hand, some adherents of a strongly descriptive approach may argue that prescription is always undesirable. Sometimes they see it as reactionary or stifling. A "pure descriptivist" believes that no language form can ever be incorrect and that advice on language usage is always misplaced. However, this is a very rare position. Most of those who claim to oppose prescription per se are in fact only inimical to those forms of prescription not supported by current descriptive analysis.