Beta

1 : the 2d letter of the Greek alphabet -- see ALPHABET table
2 : BETA PARTICLE
3 : a measure of the risk potential of a stock or an investment portfolio expressed as a ratio of the stock's or portfolio's volatility to the volatility of the market as a whole
4 : a nearly complete prototype of a product (as software)

Beta versions always disappear.

PS - Twitter, I'm thinking we might need to break up. You're not the person I thought you were.

Hmmm....