Twice as much; the state or amount that is double (or a multiple indicating how many times larger). Used in expressions like “2倍” or “〜の倍.”
今年の売上は去年の2倍になった。
This year's sales have become twice last year's.
彼は私の2倍の背がある。
He is twice my height.
二人分の料理を頼んだので、量が倍になった。
Because we ordered food for two people, the amount doubled.
A counter meaning “-fold” or “times” as in measuring how many times larger/smaller something is (e.g. 3-fold, 10-fold).
値段が3倍になってしまった。
The price has become three times as much.
この新しい製品は従来品より性能が5倍良いと宣伝している。
This new product is advertised as having performance five times better than the conventional one.
データ容量は10倍に増加した。
The data capacity increased tenfold.
Used for odds or likelihoods to indicate a ratio such as “1 in n” (e.g. 40倍 meaning odds of 1 in 40).
このくじの当選確率は40倍（＝40分の1）だ。
The winning probability for this lottery is 40 to 1 (i.e. 1/40).
倍率が高いので、合格は難しい。倍率は100倍近くになっている。
Because the odds are high, passing is difficult. The odds are close to 100 to 1.