From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

A — 1: Μέσος (Strong'S #3319 — Adjective — mesos — mes'-os )

an adjective denoting "middle, in the middle or midst," is used in the following, in which the English requires a phrase, and the adjectival rendering must be avoided:  Luke 22:55 , "Peter sat in the midst of them," lit., "a middle one of (them):"  Luke 23:45 , of the rending of the veil "in the midst;" here the adjective idiomatically belongs to the verb "was rent," and is not to be taken literally, as if it meant "the middle veil;"  John 1:26 , "in the midst of you (standeth One)," RV (lit., "a middle One");  Acts 1:18 , where the necessity of avoiding the lit. rendering is obvious. Cp. the phrases "at midday," "at midnight" (see Midday , Midnight , above). Notes: (1) Mesos is used adverbially, in prepositional phrases, (a) ana m., e.g.,  1—Corinthians 6:5 , "between;"  Matthew 13:25 , "among;"  Revelation 7:17 , "in the midst;" (b) dia m., e.g.,  Luke 4:30;  17:11 , "through the midst;" (c) en m.,  Luke 10:3 , RV, "in the midst," AV, "among;" so  Luke 22:27;  1—Thessalonians 2:7; with the article after en, e.g.,  Matthew 14:6 , RV, "in the midst," AV, "before;" (d) eis m.,  Mark 14:60 , "in the midst;" with the article, e.g.,  Mark 3:3 , "forth" (lit., "into the midst"); (e) ek m., "out of the way," lit., "out of the midst,"  Colossians 2:14;  2—Thessalonians 2:7 , where, however, removal is not necessarily in view; there is no accompanying verb signifying removal, as in each of the other occurrences of the phrases; with the article, e.g.,  1—Corinthians 5:2;  2—Corinthians 6:17; see WAY; (f) kata m.,  Acts 27:27 , "about mid(night)."

 Matthew 14:24 Philippians 2:15  Revelation 8:13Heaven

B — 1: Μεσόω (Strong'S #3322 — Verb — mesoo — mes-o'-o )

"to be in the middle," is used of time in  John 7:14 , translated "when it was ... the midst (of the feast)," lit., "(the feast) being in the middle."

Vine's Expository Dictionary of OT Words [2]

Tâvek ( תָּוֶךְ , Strong'S #8432), “midst; middle.” This word, which also appears in Ugaritic, occurs about 418 times in biblical Hebrew and in all periods.

Tâvek indicates the part of a space, place, number of people, things, or line which is not on the end or outside edge. This emphasis is in Gen. 9:21: “And he [Noah] drank of the wine, and was drunken; and he was uncovered within [literally, “in the midst of”] his tent. In many contexts the word means “among,” not necessarily in the middle: “… And he [Pharaoh] lifted up the head of the chief butler and of the chief baker among [literally, “in the midst of”] his servants” (Gen. 40:20). Exod. 14:29 uses tâvek as an extension of the word “through”: “But the children of Israel walked upon dry land in the midst of the sea.…” The idea “within” can be emphasized with the addition of words like tâvek , “belly, inwards,” or leb , “heart”: “… My heart is like wax, it is melted in the midst of my bowels” (Ps. 22:14). This word also sometimes means simply “in” in the sense of “mixed into something”: “And they did beat the gold into thin plates, and cut it into wires, to work it in the blue …” (Exod. 39:3).

Tâvek can mean “middle” when applied to an object or person between two others: “And they made bells of pure gold, and put the bells between the pomegranates upon the hem of the robe …” (Exod. 39:25). The same sense but a different translation is required in Judg. 15:4: “And Samson went and caught three hundred foxes, and took firebrands, and turned tail to tail, and put a firebrand in the midst between two tails.” This appears to be the meaning of the word in its first biblical occurrence: “And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters” (Gen. 1:6). In Num. 35:5 the word means “in the center”: “And ye shall measure from without the city on the east side two thousand cubits, and on the south side two thousand cubits, and on the west side two thousand cubits, and on the north side two thousand cubits; and the city shall be in the midst.…” In other passages this word signifies the hypothetical center line dividing something into two equal parts: “And he [Abraham] took unto him all these, and divided them in the midst, and laid each piece one against another …” (Gen. 15:10; cf. Ezek. 15:4).

In a few instances tâvek is used substantively, meaning “the middle or the center part of a thing”: “Sihon king of the Amorites … ruled from Aroer, which is upon the bank of the river Arnon, and from the middle of the river …” (Josh. 12:2). The word occurs only 7 times without a preceding preposition.

King James Dictionary [3]

Midst n. contracted from middest, the superlative of mid.

The middle.

There is nothing said or done in the midst of the play, which might not have been placed in the beginning.

The phrase, in the midst, often signifies involved in, surrounded or overwhelmed by, or in the thickest part, or in the depths of as in the midst of afflictions, troubles or cares in the midst of our contemplations in the midst of the battle in the midst of pagan darkness and error in the midst of gospel light in the midst of the ocean in the midst of dissensions.

From the midst, from the middle, or from among.  Deuteronomy 18

MIDST, adv. In the middle.

On earth,join all ye creatures to extol

Him first, Him last, Him midst, and without end.

Webster's Dictionary [4]

(1): ( n.) The interior or central part or place; the middle; - used chiefly in the objective case after in; as, in the midst of the forest.

(2): ( adv.) In the middle.

(3): ( n.) Hence, figuratively, the condition of being surrounded or beset; the press; the burden; as, in the midst of official duties; in the midst of secular affairs.

(4): ( prep.) In the midst of; amidst.