Learn Arabic (Modern Standard): المطعم مفتوح لكن الطعام بارد. - The restaurant is open but the food is cold.

لكن (lakin) is used to show contrast, just like "but" in English. In this sentence, it simply acts as a bridge connecting two complete, independent statements: المطعم مفتوح (The restaurant is open) and الطعام بارد (the food is cold).

Why isn't there a word for "is" in this sentence?

In Arabic, the present-tense verbs for "is" or "are" are usually implied rather than written out. A sentence starting with a noun, like المطعم مفتوح (The restaurant [is] open), naturally creates that "is" meaning between the subject and the describing word. This is called a nominal sentence.

Why do المطعم (the restaurant) and الطعام (the food) have الـ (the) attached, but مفتوح (open) and بارد (cold) do not?

This is how Arabic separates a full sentence from a simple descriptive phrase. Because the adjectives مفتوح and بارد do not have الـ (al-), they act as the "news" or predicate about the nouns. If they both had الـ (like المطعم المفتوح), it would just mean the phrase "the open restaurant" instead of the full sentence "The restaurant is open."

The words for "restaurant" (المطعم) and "food" (الطعام) look similar. Are they related?