Learn Dutch: De witte schoenen zijn goedkoop.

witte comes directly before the noun it describes (schoenen). In Dutch, adjectives in this position almost always get an -e added to them. goedkoop comes after the verb (zijn). Adjectives used later in the sentence like this stay in their basic dictionary form and never get the extra -e.

The dictionary word for "white" is wit. Why is it spelled with double T in witte?

This is because of a Dutch spelling rule to keep the vowel sound short. If we just added an -e to get "wite", the i would change to a long vowel sound (like in the English word "we"). Doubling the consonant to tt locks in the short i sound.

How do we know schoenen means "shoes" plural, rather than just one shoe?

The singular word for shoe is schoen. Dutch usually makes words plural by adding -en to the end. The verb zijn (are) also matches this plural form.

If we said "White shoes" instead of "The white shoes", would witte still have the -e ending?