This root carries two threads that braid together in Hebrew. One is the number seven, and from seven comes the week (שָׁבוּעַ), since a week is seven days, and the oath (שְׁבוּעָה), because in the Bible to swear was to "seven oneself". The other thread is satiety, being full of food (שָׂבֵעַ). Notice the spelling: the satiety branch starts with שׂ (sin), the seven/oath branch with שׁ (shin). Same three letters, two cousins. Every entry is verified against pealim, niqqud included.
The same root runs through the verb system. Each binyan is a voice: it bends the one idea into active, passive, causative or reciprocal. Tap to hear.
Only the satiety branch (שׂ, sin) produces live verbs: pa'al is being full yourself, hif'il is the causative, filling someone up. The seven/oath branch (שׁ, shin) shows up almost entirely as nouns, adjectives, and the numeral, not as verbs in everyday Hebrew. Other binyanim are not lexicalized for this root.
Same root letters, different noun moulds (mishkalim). The mould tells you the function: who does it, the act of doing it, or the thing produced.
Strip the prefixes, suffixes and vowels. Three consonants remain, and the meaning lives there.