Learn Russian: Обед готов.

Готов is a short-form adjective. In Russian, we often use short forms to describe temporary states or conditions. Since the lunch being ready is a temporary state, we use готов instead of the full-form adjective готовый.

How does the word готов agree with обед here?

Short-form adjectives must match the gender and number of the noun they describe. Because обед is a masculine singular noun (it ends in a consonant), we use the basic masculine short form готов. If the subject were feminine, like пицца (pizza), we would use готова.

Where is the verb for "is" in this sentence?

In the present tense, Russian drops the verb "to be" (am, is, are). You simply place the subject (обед) and the adjective (готов) next to each other. If this were in the past tense ("Lunch was ready"), you would need to add the past-tense verb был.