Lessons 29-30

the science and practice of aircraft navigation; the engineering of aircraft

infection-fighting substances derived from microorganisms

a robot; a person acting like a robot

to change; to change a penalty to a less severe one; to travel back and forth

to overcrowd ; to clog, as with mucus

thoughtful; kind; taking the needs of others into account

gradual wearing away(as of the earth's surface);deterioration

the killing of one human being by another; murder or manslaughter

moved or operated by compressing water or some other liquid

an unproven theory

to fail to function or act as expected; to function improperly; n. a failure to work as expected

living at the expense of or taking advantage of others; living on an organism and contributing nothing

having qualities that are attractive or suitable for photographing

a building with a domed ceiling onto which images of celestial bodies are projected

a partial refund; v. to give back part of an original payment

breathing; a complete breath, including inhaling and exhaling

artificial; made by chemical process to imitate a natural product

the technical methods of applying scientific and and industrial skills to practical uses; applied science

of great size, strength, or power

an assurance or guarantee by the seller that a product will maintain a certain standard of performance or else be replaced or repaired