Questions & Answers about Мой телефон дороже, чем книга.
Russian has two ways to form comparatives of adjectives:
• Synthetic comparatives (one-word forms): дороже, моложе, старше, быстрее
• Analytic comparatives (two-word forms with более/менее): более дорогой, менее дорогой
For most common adjectives—especially those with one or two syllables—the synthetic form (дороже) is more idiomatic and concise. The analytic form (более дорогой) exists and is perfectly correct, but it sounds heavier in everyday speech.
Morphologically, дорогой → дороже is formed by:
- Dropping the ending -ой
- Softening the stem consonant г → ж (a regular phonetic change)
- Adding the comparative ending -е
So дорог- + ж + е = дороже.
In Russian, when you introduce a comparison with the conjunction чем (“than”), you treat the second part as a subordinate clause. Standard punctuation rules require a comma before чем to mark the boundary:
Мой телефон дороже, чем книга.
↑ comma here
Omitting this comma in writing is considered non-standard, though in rapid speech it may not be pronounced distinctly.