שוב

Abarim Publications' online Biblical Hebrew Dictionary

שוב ישב שבת שבה

There appears to be a slight to strong kinship between the meanings of the four root forms שוב (shub), ישב (yashab), שבת (shabbat) and שבה (shaba). And their forms are so adjacent that the effects of conjugation and grammatical constructions sometimes obscure the exact origin of derived words or names. Roots and meanings of words in narrative text can usually be estimated by their contexts, but even when these are clear, the interpreter should always keep an eye on the other roots and keep an open mind for alternative translations.

The verb שוב (shub) generally means to turn back or to return. This very common verb (HAW Theological Wordbook of the Old Testament says it's the twelfth most frequently occurring verb in the Old Testament) is used in the regular, expectable sense of physically turning around and going back to some place (Numbers 23:5, Judges 3:19). But mostly it refers to a mental or spiritual returning, away from evil and vice, and towards virtue and God (Numbers 14:43, Hosea 6:1).

Secondary meanings include repetition (Genesis 26:18), restoration (Isaiah 52:8), rescue (Genesis 14:16), retrieval (Genesis 38:29), abstinence (Lamentations 2:8), requital (1 Samuel 6:8), reply (Exodus 19:8), repulse (Jeremiah 2:24), and reconsideration (Lamentations 3:21).
This verb's derivatives are:

The feminine noun שובה (shuba) meaning retirement or withdrawal (Isaiah 30:15 only).
The feminine noun שיבה (shiba) meaning restoration (Psalm 126:1 only).
The adjective שובב (shobab) meaning backsliding (Isaiah 57:17, Jeremiah 3:14).
The similar adjective שובב (shobeb), also meaning backsliding (Micah 2:4, Jeremiah 31:22).
The feminine noun משובה (meshuba), meaning backsliding as well (Hosea 14:5, Jeremiah 2:19).
The feminine noun תשובה (teshuba) meaning answer (Job 34:36) or return (2 Samuel 11:1).

ישב

The primary meaning of the verb ישב (yashab) seems to be to sit, and as such it became to also denote to remain or to dwell. This very common verb is deployed in all the expectable contexts, from sitting on a chair (1 Samuel 20:25), to God being enthroned (Psalm 8:7), to doing one's business (Deuteronomy 23:14). And from hanging out a few days (Genesis 27:44) to remaining at peace for three years (1 Kings 22:1). It may tell of people settling somewhere (Genesis 4:16), or of animals inhabiting a ruined city (Jeremiah 50:39). In rare instances, it may even mean to marry (Ezra 10:2, Nehemiah 13:27), but that's probably to be understood as 'to give dwelling to.'

This verb's derivatives are:

The feminine noun שבת (shebet), meaning seat (1 Kings 10:19), or dwelling (Numbers 21:15). Note the striking similarity between this word and the noun שבת (shebbet) derived of the root שבת (shbt; see next)
The feminine noun שיבה (shiba), meaning sojourn (2 Samuel 19:33 only).
The masculine noun מושב (moshab), meaning a seat (1 Samuel 20:18), a dwelling place or territory (Genesis 10:30), or a location of something (a city - 2 Kings 2:19; an image - Ezekiel 8:3), the period of staying somewhere (Exodus 12:40), or a group of people that is dwelling somewhere (2 Samuel 9:12).
The masculine noun תושב (toshab), meaning sojourner (Genesis 23:4, Exodus 12:45).

שבת

It's not clear whether the feminine noun שבת (shabbat) (=Sabbath) was derived from the verb שבת (shabat), meaning to cease or to rest, or vice versa. But the verb שבת (shabat) only means to repose when it's used in connection to the Sabbath. In all other contexts it means to sever or put an end to (Genesis 8:22, Jeremiah 31:36).

Other derivatives are:

The feminine noun שבת (shebbet), which is difficult to translate but basically means cessation (Isaiah 30:7, Proverbs 20:3). Note the similarity between this noun and the noun שבת (shebet), meaning seat, mentioned above.
The masculine noun משבת (mishbat) also meaning cessation (Lamentations 1:7 only).
The denominative verb שבת (shabat) means to keep the Sabbath (Leviticus 23:32 and 25:2 only).
The masculine noun שבתון (shabbaton) denotes a sabbatical observance and is used in relation to keeping the Sabbath, the day of atonement (Leviticus 16:31), feast of trumpets (Leviticus 23:24) and the first and eighth day of the feast of booths (Leviticus 23:39).

שבה

The verb שבה (shaba) means to take captive (Numbers 24:22, 2 Chronicles 21:17), or in the words of HAW Theological Wordbook of the Old Testament: this verb "conveys the idea of a military or paramilitary force subduing a foe and then taking into their possession the men, women, children, cattle and wealth of the defeated party". In the New Testament this military term came to illustrate Jesus' redemptive mission of setting the captives [of sin] free (Luke 4:18, quoting Isaiah 61:1).

This verb's derivatives are:

The masculine noun שבי (shebi), meaning captivity (Nahum 3:10), the act of capture (Amos 4:10) or captives collectively (Exodus 12:29).
The feminine noun שביה (shebiya), meaning captive (Isaiah 52:2).
The feminine noun שביה (shibya), meaning captivity (Jeremiah 48:46) or captives collectively (Deuteronomy 21:11).
The feminine noun שבית (shebit) or שבות (shebut), meaning captivity (Numbers 21:29), or, curiously, restoration (Ezekiel 16:53, Job 42:10).
The feminine noun שבו (shebo), denoting some kind of gem stone that was put in the breastplate of the priestly ephod. Its derivation is uncertain. It may be a Hebrew transliteration of a foreign word, or perhaps this stone was known as a 'captivator' to the Hebrews.