a rapidly increasing body of knowledge concerning

a Determinative

— A is used when the following word could be any of a certain type. Compare "A book I saw on the shelf" and "The book I gave you yesterday".

a Noun

— A is the first letter of the alphabet. The letter "a" comes before "b". — In some schools, an A is a very high grade. Ron got an A on his earth science test.

rapidly Adverb

— If something is done rapidly, then it is done quickly or swiftly.

increasing Adjective

— If something is increasing, it is growing bigger. He is worried about his increasing debt: it keeps getting bigger and bigger.

body Noun

— A body is the main part of a person, animal, physical object, or organisation. After falling out of the tree, his arm was broken and his body hurt all over. The governing body of the UN meets in Geneva. — A body is a dead person or animal. The police found her body after she had been missing for three days. — A body is a group of people. The senate is an important legislative body in the United States. — A body of something is a lot on it together in one place. Lake Michigan is a large body of water. — A body is a thing that all moves together. The moon is a body in orbit around Earth.

of Preposition

— Made using. It is a house of cards.

knowledge Noun

— Knowledge is information that you know. He shared his knowledge with you.

concerning adjective

— Causing concern; worrisome. — (obsolete) Important.

concerning preposition

— regarding

concerning noun

— That which one is concerned in; one's business.