To answer your question: Yes, in general, adjectives with only one syllable receive the -er suffix when making comparisons. Words with two syllables, like the word "happy," may also receive the -er suffix when making comparisons. For example, "People who walk are happier than people who drive." The important thing to remember here is that while most adjectives with a single syllable will take on -er endings, whether or not a larger word takes on an -er ending depends on the word itself. I hope that I was able to help you out.

Here are some more 2 syllable words that can go either way: commoner / more common stupider / more stupid handsomer / more handsome Basically, if you can add "-er" and still pronounce the new word as just two syllables ("comm'ner," "stup'der," "hand'mer") you may do so. On the other hand, there are some one-syllable adjectives that generally take "more." For example, verb participles like "more browned," more "hurt." Also, one syllable words ending in "r" often take "more" -- example: "more clear." This is "incorrect," but many people (at least in the US) do this to avoid repeating the "r."

usually if it has 1-2 syllables you add -er mild - milder hot - hotter cold - colder bright - brighter but of course with 2 syllables there are exceptions happy - happier nosy - nosier 3 or more syllables you add (more) interesting - more interesting exciting - more exciting