Learn Icelandic: Þessi risaeðla er allra stærst! - This dinosaur is the very biggest!

The word allra is the genitive plural form of allur (all), literally meaning "of all." When placed right in front of a superlative adjective, it acts as an intensifier. Instead of just meaning "biggest," it elevates the meaning to "the biggest of all" or "the very biggest."

Why does the sentence use the strong form stærst instead of the weak form stærsta?

Because the adjective comes after the verb er to describe the subject. Even though we translate it as "the biggest" in English, Icelandic uses the strong feminine nominative singular stærst here to match risaeðla. You would only use the weak form if it were acting as part of a definite noun phrase, like in stærsta risaeðlan (the biggest dinosaur).

Since learners often use þetta to mean "this," why is it þessi here?

When "this" is attached directly to a noun ("this dinosaur"), it must agree with that noun's gender and number. Since risaeðla is a feminine noun, we need the feminine nominative singular þessi. You would use the uninflected neuter þetta for a standalone pointer, such as Þetta er risaeðla (This is a dinosaur).

What are the root words that make up the word risaeðla?