You already know that superlatives usually end in -ast (or -st for irregular adjectives). When you put a superlative directly in front of a specific noun—like "the fastest winner" or "the toughest race"—you must use the definite form.
Just like basic adjectives, superlatives require the "double definite" pattern: a free definite article (den for en words, det for ett words), a special ending on the superlative, and the noun in its definite form.
Regular Superlatives (-aste)
For regular adjectives that end in -ast in the superlative, the definite ending is always -e. This makes the full ending -aste, and it applies to all nouns regardless of gender.
| The fastest winner takes the medal. | Den snabbaste vinnaren tar medaljen. |
| It was the toughest race in the world. | Det var det tuffaste loppet i världen. |
Irregular Superlatives (-sta / -ste)
Many short or irregular adjectives change their vowel and end in just -st in their superlative form (such as ung → yngst or lång → längst).
For these adjectives, the standard definite ending is -a (making the ending -sta). However, when describing a specific male person, the ending changes to -e (making it -ste).
Notice how yngst becomes yngste and bäst becomes bäste for a male person:
| The youngest brother is the best champion. | Den yngste brodern är den bäste mästaren. |
In the following sentence, you can see both rules side by side. The irregular äldst takes the standard -a ending for a house, while the regular rikast keeps its mandatory -e ending.
| We visited the oldest house where the richest man had lived. | Vi besökte det äldsta huset där den rikaste mannen hade bott. |
| The fastest dog wins the longest race. | Den snabbaste hunden vinner det längsta loppet. |