Quick definition
An options Greek measuring time decay — the daily erosion of an option's value as expiration approaches. Theta accelerates in the final weeks before expiration.
The acceleration curve
Theta is not linear. It accelerates as expiration nears, with the steepest decay in the final three to four weeks. A long-dated LEAPS contract loses very little per day; a weekly option a few days from expiration can lose 10% of its value overnight. This is why credit (premium-selling) strategies typically open positions inside 45 days to expiration.
Long vs short theta
Premium sellers want time to pass — they're short theta and collect decay daily. Premium buyers fight time — they need a directional move large and fast enough to overcome continuous theta bleed. Most retail options losses come from underestimating how aggressively theta works against long OTM calls and puts.
How Treeova uses it
Treeova's Adaptive Risk Engine accounts for theta acceleration when sizing stop-loss buffers near expiration — a static dollar stop on a high-theta position is mechanically wrong. The Triconomic Engine also displays per-position theta in the cockpit so traders can see, daily, how much of their P&L came from decay vs directional movement.