Cheap to run; using minimal resources; representing good value for money; economical.

(US) In or via the part of a commercial passenger airplane reserved for those paying the lower standard fares.

A scholar of ecology. / (uncommon) An environmentalist (one who advocates for the protection of the environment).

(medicine, slang) Deep vein thrombosis.

(cricket) A bowler's statistic, being the average number of runs conceded per over.

(economics, mathematics) A sub-field of economics which aims at expressing economic theories with mathematic formulae.

Pertaining to an economy. / Frugal; cheap (in the sense of representing good value); economical. / Pertaining to the study of money and its movement.

(intransitive) To practice being economical (by using things sparingly or in moderation, and by avoiding waste or extravagance). / (transitive) To use frugally.

A large concrete block with a groove in the bottom face and a tongue on the top face to eliminate slippage when they are stacked. There is also a steel loop on the top face to facilitate lifting. The blocks are stacked in an offset manner to create a wall for retaining earth by means of their great mass. A wall built with them can be readily dismantled and the blocks reused (in ecological fashion).

A system formed by an ecological community and its environment that functions as a unit. / The interconnectedness of organisms (plants, animals, microbes) with each other and their environment.