As a general rule, most other two-syllable adjectives also form comparatives and superlatives with more and most, apart from those ending in -y. However, a few two-syllable adjectives can take either -er/-est or more/most. Here are three examples.
narrow narrower/more narrow the narrowest/most narrow
simple simpler/more simple the simplest/most simple
quiet quieter/more quiet the quietest/most quiet
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