The periods unit of punctuation marks.

A punctuation, ., which is placed at the end of a declarative sentence to indicate a full stop or after abbreviations.

A period of 63 days in the dog, from fertilization to whelping.

A period when writing systems existed.

The historic period in any particular region begins when writing systems emerge or when literate cultures come into contact with the regions preliterate inhabitants.

A relation obeyed by cepheid variable stars (highly luminous yellow or orange super giant stars that varies regularly in brightness), and which states that the period of the changes in luminosity varies directly with the luminosity of the star.

The time required for a celestial body in the solar system to complete one revolution with respect to the fixed stars (as observed from a fixed point outside the system).

A planet's sidereal period can be calculated from its synodic period or the length of time during which a body in the solar system makes one orbit of the sun relative to the earth.

The sidereal period of the moon or an artificial satellite of the earth is the time it takes to return to the same position against the background of stars.

1. The length of time during which a body in the solar system makes one orbit of the sun relative to the earth; that is, returns to the same elongation. 2. The time required for a body in the solar system to return to the same or about the same position relative to the sun as seen from the earth.

A period is a single small dot at the end of a group of words that have been written and it means that this is the end of a complete statement or sentence.

The period is a warning to the reader that the statement is finished and so it must not be run together with whatever follows it.

The idea that is stated in the sentence, or group of words, begins with a capital letter and ends with a period which is presented in the form of a simple assertion.

The writer does not intend to ask the reader a question, nor does he or she want the reader to feel that the sentence is expressing a thought with great emphasis. It is simply stated and that's what the period tells readers.

That is all anyone needs to know about the single little dot which is used as a mark of punctuation and is called a period. Oh, yes, remember that when an abbreviation occurs at the end of a sentence, or a statement, the abbreviation point and the period are combined into one dot and so the use of two dots is not necessary nor acceptable in normal English writing.

Fat little period, round as a ball,
You'd think it would roll,
But it doesn't
At all. Where it stops,
There it plops,
There it stubbornly stays,
At the end of a sentence
For days and days.

"Get out of my way!"
Cries the sentence. "Beware!"
But the period seems not to hear or to care.
Like a stone in the road,
It won't budge, it won't bend.
If it spoke, it would say to a sentence,
"The end."