Maximum supply

Maximum supply is the ceiling written into a token's rules: no matter how much time passes or how many blocks are produced, issuance stops once that number is reached. In Bitcoin the limit is not stored as a single constant but follows from the block reward halving every 210,000 blocks, which makes total issuance converge just below 21 million BTC.

The figure matters because it is the denominator behind fully diluted valuation and the basis of scarcity arguments. Data sites list it next to circulating supply, the coins actually in the market, and total supply, the coins created so far, and the gap between the three tells you how much dilution may still be ahead.

Not every asset has one. Ether and Dogecoin have no fixed cap, and many tokens give an admin or governance the power to change minting rules, so a stated maximum is only as firm as the code and the people who control it. Lost coins also mean the effective supply ends up lower than the cap.