Noun

(en-noun)

(uncountable) Any substance that can be consumed by living organisms, especially by eating, in order to sustain life.

* {{quote-book, year=1922, author=(Ben Travers), title=(A Cuckoo in the Nest)

, chapter=1 citation , passage=“[…] the awfully hearty sort of Christmas cards that people do send to other people that they don't know at all well. You know. The kind that have mottoes like
  Here's rattling good luck and roaring good cheer, / With lashings of food and great hogsheads of beer. […]”}}

* {{quote-magazine, date=2013-06-29, volume=407, issue=8842, page=72-3, magazine=(The Economist)

, title= A punch in the gut , passage=Mostly, the microbiome is beneficial. It helps with digestion and enables people to extract a lot more calories from their food than would otherwise be possible. Research over the past few years, however, has implicated it in diseases from atherosclerosis to asthma to autism.}}

(countable) A foodstuff.

(uncountable, figuratively) Anything that nourishes or sustains.

Mozart and Bach are food for my soul.

* (and other bibiographic particulars) (William Shakespeare)

This may prove food to my displeasure.

* (and other bibiographic particulars) (William Wordsworth)

In this moment there is life and food / For future years.

Noun

The branch of biology dealing with the relationships of organisms with their environment and with each other.

* 1949 - Bruce Kiskaddon, George R. Stewart

As a graduate student, he was working on a thesis: The Ecology of the Black Creek Area . He had to investigate the relationships, past and present, of men and plants and animals in this region.

* {{quote-magazine, date=2012-01

, author=Robert M. Pringle , title=How to Be Manipulative , volume=100, issue=1, page=31 , magazine= citation , passage=As in much of biology, the most satisfying truths in ecology derive from manipulative experimentation. Tinker with nature and quantify how it responds.}}