Errors in the use of adjectives and adverbs commonly occur when making comparisons. Below, Grammarly has identified two of the most common types of mistake:

The student has written the following:

Some forms of intelligence are more unique than others. A person with math skills, however, is not more smarter than an artistic person.

There are two errors in this excerpt. The first sentence contains the word unique, an adjective which never has a comparative form. Something is either "unique" or "not unique," but it cannot be "more unique" or "less unique" than something else (other adjectives that have this property include "perfect," "round," and "extinct"). The student could fix the error in the first sentence by writing,

Some forms of intelligence are rarer than others.

The second sentence contains an error in adjective comparison. Comparative adjectives are formed either by changing the adjective’s ending ("big," "bigger," "biggest") or by adding a word to indicate degree ("careful," "more careful," "most careful"). Using both strategies, as the second sentence does—"more smarter"—is incorrect. The student should fix this error by writing,

A person with math skills, however, is not smarter than an artistic person.

Note: In general, adjectives of one syllable change endings ("smart," "smarter," "smartest"), and adjectives of more than one syllable take additional words ("intelligent," "more intelligent," "most intelligent").