Thia dog is old.
older, the oldest
This dog has short hair.
shorter, the shortest
This is a small dog.
smaller, the smallest
This dog is big.
bigger, the biggest
This dog has long hair.
longer, the longest
This is a gentle dog.
gentler, the gentlest
This dog is young.
younger, the youngest
This dog is vicious.
more vicious, the most vicious