Plain-English definition
Whoever builds a block decides the order of the transactions in it. That power can be sold: front-run a large trade, sandwich it, or capture an arbitrage. The value squeezed out this way is MEV.
Some MEV is benign arbitrage that keeps prices aligned; some is a tax extracted from ordinary users. Either way it is a real, measurable force in how blocks get built.
Why it matters
MEV (Maximal Extractable Value) matters because crypto markets can look precise while still being shallow, crowded, or poorly sourced. A useful read is not just the number. It is the number, the size behind it, the context around it, and the part it cannot explain.
Simple example
A simple MEV (Maximal Extractable Value) example is a reader comparing two venues with the same headline price but different depth. The deeper venue can absorb more capital before the trade, peg, or yield reading starts to move against the user.
How Bathymark uses this term
Bathymark uses MEV (Maximal Extractable Value) to translate open market data into live liquidity readings. When the term touches a live page, the reading links back to the relevant chain, protocol, stablecoin, DEX, perps, or Signal so the source remains checkable.
Common mistake
The common mistake is treating MEV (Maximal Extractable Value) as a complete signal by itself. Bathymark treats it as one instrument: useful when read beside liquidity, source, size, and what the number cannot prove.