(1) The moon between the new moon and first quarter, and between the last quarter and the next new moon. (2) Anything shaped like the crescent moon.

*Crescent* means basically “growing,” since a crescent moon is in the process of “growing” to a full moon. A *crescent wrench*, with its open end (unlike the kind of wrench that has an almost circular end), can be found in almost any household. A *croissant,* or crescent pastry, is a breakfast staple. The curving region called the Fertile Crescent, which stretches from the Persian Gulf up through Iraq, across to Lebanon and Israel, and down into Egypt's Nile River valley, was the birthplace of civilization, where weaving, pottery, domesticated livestock, irrigation farming, and writing all first appeared.

(1) Growth or enlargement by gradual buildup. (2) A product of such buildup.

The slow accretion of scientific knowledge over many centuries has turned into an avalanche in our time. Any accretion of ice on a grounded jet will result in takeoff delays because of the danger it poses. The land area of the Mississippi Delta increases every year from the accretion of soil washed down the Mississippi River, though the accretions happen so slowly that it's difficult to detect any increase at all. *Accretion* is often used in scientific writing; its usual verb form, *accrue*, is more often used in financial contexts (“This figure doesn't count the accrued interest on the investments”).

(1) A projection of growth, especially when abnormal. (2) A disfiguring, unnecessary, or unwanted mark or part.

Warts and pimples are common excrescences that can usually be wiped out with medication; other excrescences such as cysts and tumors need to be removed surgically. Mushrooms are the excrescences of underground fungus networks. Some people consider slang words to be vulgar excrescences on the English language, but others consider slang the most colorful vocabulary of all.

(1) Something gained or added, especially as one of a series of regular additions or as a tiny increase in amount. (2) The amount or extent of change, especially the positive or negative change in value of one or more variables.

*Increment* is used in many technical fields, but also nontechnically. *Incremental* increases in drug dosages are used for experimental purposes. Incremental tax increases are easier to swallow than sudden large increases. Incremental changes of any kind may be hard to notice, but can be very significant in the long run. Rome wasn't built in a day, but was instead built up by increments from a couple of villages in the 10th century B.C. to the capital of the Mediterranean world in the 1st century A.D.

(1) The process of transferring a fluid and especially blood into a blood vessel. (2) Something transfused.

When blood transfusions were first attempted by Europeans in the early 1600s, they were met with skepticism, since the established practice was to bleed patients, not *transfuse* them with blood. Some patients were transfused with animal blood, and so many died as a result that by 1700 transfusions had been widely outlawed. Not until 1900 were the major blood groups (A, B, AB, and O) recognized, making transfusions safe and effective.

(1) Given to excessive display of feeling. (2) Freely expressed.

Since to *effuse* is to “pour out,” an effusive person makes a habit of pouring out emotions. Greeting someone *effusively* may include great hugs and wet kisses. Academy Award winners tend to become embarrassingly effusive once they've got the microphone. But at least *effusiveness* is generally an expression of positive rather than negative emotions.

Great abundance.

A profusion is literally a “pouring forth,” so a profusion of gifts is a wealth or abundance of gifts. A *profusely* illustrated book is filled to overflowing with pictures. A bad social error should be followed by *profuse* apologies, and profound gratitude should be expressed with profuse thanks.

To spread over or fill something, as if by fluid or light.

The odors of baking may suffuse a room, and so may the light of a sunset. A face may be suffused (that is, filled, but also probably flushed) with joy, or hope, or love. A novel may be suffused with Irish humor, and a room may be suffused with firelight. Scientists may even describe an insect's gray wings as being suffused with tinges of red.