How do I identify a position as open, semi-open, or closed?

Any thoughts would be much appreciated!

That's how I understand it...

Yeah, better :)

Maybe open positions come from "Open" openings 1 e4 45, Semi Open from semi open openings 1 e4 anything except e5, and closed from d4 and other openings?

Generally, open games start with e4..e5, and closed games start with d4..d5.

Semi-open: e4..other, semi-closed: d4..other.

That's only generally though. It depends on if the pieces are in front of the pawns in the middle game or behind them.

Very interesting! Thanks very much!  That helps a lot.

Oook.  That makes sense- more sense.  I feel this will help me to identify where I struggle most in chess so am glad I was able to get such detailed explanations!

The easiest way to tell is this:

If my knights are kicking your butt, it's probably closed.

If it's my bishops, probably open.

(Of course, if it's both, semi-open.)

lol jk

1.e4 e5 isn't always open, 1.d4 isn't always closed.  1.e4 e5 can lead to the "Closed Ruy Lopez", which is more of a "Semi-Closed" defense.

Think of it this way. 

"Open" tends to see the central pawns liquidated.  The other possibility is that one flank is completely liquidated of pawns, and the pawns in the center are still fluid.  Often there are open files for Rooks to travel from one end of the board to the other.

"Semi-Open" tends to see one or two pawns by each player traded off, often on different files.  For example, in the Sicilian, cxd4, White has a half-open d-file while black has a half-open c-file.  The board isn't locked up, but heavy pieces don't go flying across the board nearly as easily.

"Semi-Closed" tends to see very few, if any, pawns traded off, but there is still the opportunity for it to open up.  An example would be lines of the Nimzo-Indian with an early ...d5.  Fireworks aren't going off yet, but theys till can.

"Closed" tends to see no pawn trades, and the center completely locked.  The best example of this is the Classical King's Indian Defense.  1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 O-O 6.Be2 e5 7.O-O Nc6 8.d5 Ne7 9.Ne1 Nd7 10.Be3 (or 10.Nd3 is also an option) f5 11.f3 f4 12.Bf2 g5.  Notice how locked up the center is.  Closed positions tend to lead to opposite wing attacks.  Here, White attacks Queenside, Black attacks Kingside.  Closed positions usually feature a concept called "Pawn Pointing".  No matter where your own King is, or your opponent's, you should attack the side in which your pawns point.  In the example above, the White pawns point towards the Queenside, the Black pawns toward the Kingside.  A common example of the opposite scenario is the Advance Variation of the French Defense, where White attacks Kingside, and Black Queenside, even in the lines where White plays 6.a3 and Black responds with 6...c4.  Black will castle Queenside, White Kingside, but even then, Black should attack the Queenside, and White the Kingside.

Hope this helps.