(Geol.) A period in the American eocene, the lowest in the tertiary age except the lignitic. [ 1913 Webster ]

n. (Med.) A remedy possessing the property of preventing the return of periodic paroxysms, or exacerbations, of disease, as in intermittent fevers. [ 1913 Webster ]

(Geol.) The closing subdivision of the Devonian age in America. The rocks of this period are well developed in the Catskill mountains, and extend south and west under the Carboniferous formation. See the Diagram under Geology. [ 1913 Webster ]

(Geol.) A subdivision of the Quaternary age immediately following the Glacial period; -- so named from beds near Lake Champlain. [ 1913 Webster ]

☞ The earlier deposits of this period are diluvial in character, as if formed in connection with floods attending the melting of the glaciers, while the later deposits are of finer material in more quiet waters, as the alluvium. [ 1913 Webster ]

(Geol.) A subdivision in the upper part of the Devonian system in America, so named from the Chemung River, along which the rocks are well developed. It includes the Portage and Chemung groups or epochs. See the Diagram under Geology. [ 1913 Webster ]

(Geol.) A subdivision of the Devonian system of America; -- so named from Hamilton, Madison Co., New York. It includes the Marcellus, Hamilton, and Genesee epochs or groups. See the Chart of Geology. [ 1913 Webster ]

(Geol.) A subdivision or the American Upper Silurian system, embracing the Medina, Clinton, and Niagara epoch. The rocks of the Niagara epoch, mostly limestones, are extensively distributed, and at Niagara Falls consist of about eighty feet of shale supporting a greater thickness of limestone, which is gradually undermined by the removal of the shale. See Chart of Geology. [ 1913 Webster ]

n. [ L. periodus, Gr. peri`odos a going round, a way round, a circumference, a period of time; peri` round, about + "odo`s a way: cf. F. période.] 1. A portion of time as limited and determined by some recurring or cyclic phenomenon, as by the completion of a revolution of one of the heavenly bodies; a division of time, as a series of years, months, or days, in which something is completed, and ready to recommence and go on in the same order; as, the period of the sun, or the earth, or a comet; the period of an electromagnetic wave is the time interval between maxima. [1913 Webster]

2. Hence: A stated and recurring interval of time; more generally, an interval of time specified or left indefinite; a certain series of years, months, days, or the like; a time; a cycle; an age; an epoch; as, the period of the Roman republic. [1913 Webster]

How by art to make plants more lasting than their ordinary period. Bacon. [1913 Webster]

3. (Geol.) One of the great divisions of geological time; as, the Tertiary period; the Glacial period. See the Chart of Geology. [1913 Webster]

4. The termination or completion of a revolution, cycle, series of events, single event, or act; hence, a limit; a bound; an end; a conclusion. Bacon. [1913 Webster]

So spake the archangel Michael; then paused,
As at the world's great period. Milton. [1913 Webster]

Evils which shall never end till eternity hath a period. Jer. Taylor. [1913 Webster]

This is the period of my ambition. Shak. [1913 Webster]

5. (Rhet.) A complete sentence, from one full stop to another; esp., a well-proportioned, harmonious sentence. “Devolved his rounded periods.” Tennyson. [1913 Webster]

Periods are beautiful when they are not too long. B. Johnson. [1913 Webster]

☞ The period, according to Heyse, is a compound sentence consisting of a protasis and apodosis; according to Becker, it is the appropriate form for the coordinate propositions related by antithesis or causality. Gibbs. [1913 Webster]

6. (Print.) The punctuation point [.] that marks the end of a complete sentence, or of an abbreviated word. [1913 Webster]

7. (Math.) One of several similar sets of figures or terms usually marked by points or commas placed at regular intervals, as in numeration, in the extraction of roots, and in circulating decimals. [1913 Webster]

8. (Med.) The time of the exacerbation and remission of a disease, or of the paroxysm and intermission. [1913 Webster]

9. (Mus.) A complete musical sentence. [1913 Webster]

10. (Sports) One of the specified time intervals into which a game is divided; as, there are three periods in a hockey game. [PJC]

11. (Education) One of the specified time intervals into which the academic day is divided; as, my calculus class is in the first period. [PJC]

12. The time interval during which a woman is menstruating, or the event of a single menstruation; as, her period was late this month. [PJC]

The period, the present or current time, as distinguished from all other times. [1913 Webster]

Syn. -- Time; date; epoch; era; age; duration; limit; bound; end; conclusion; determination. [1913 Webster]

v. t. To put an end to. [ Obs. ] Shak. [ 1913 Webster ]

v. i. To come to a period; to conclude. [ Obs. ] “You may period upon this, that, ” etc. Felthman. [ 1913 Webster ]

n. (Chem.) A salt of periodic acid. [ 1913 Webster ]

a. [ Pref. per- + iodic. ] (Chem.) Pertaining to, derived from, or designating, the highest oxygen acid (HIO4) of iodine. [ 1913 Webster ]

{ } a. [ L. periodicus, Gr. periodiko`s: cf. F. périodique. ] 1. Of or pertaining to a period or periods, or to division by periods. [ 1913 Webster ]

The periodical times of all the satellites. Sir J. Herschel. [ 1913 Webster ]

2. Performed in a period, or regular revolution; proceeding in a series of successive circuits; as, the periodical motion of the planets round the sun. [ 1913 Webster ]

3. Happening, by revolution, at a stated time; returning regularly, after a certain period of time. [ 1913 Webster ]

The periodic return of a plant's flowering. Henslow. [ 1913 Webster ]

To influence opinion through the periodical press. Courthope. [ 1913 Webster ]

4. Acting, happening, or appearing, at fixed or somewhat variable intervals; recurring; as, periodical epidemics [ 1913 Webster ]

5. (Rhet.) Of or pertaining to a period; constituting a complete sentence. [ 1913 Webster ]

Periodic comet (Astron.), a comet that moves about the sun in an elliptic orbit; a comet that has been seen at two of its approaches to the sun. --
Periodic function (Math.), a function whose values recur at fixed intervals as the variable uniformly increases. The trigonomertic functions, as sin(x), tan(x), etc., are periodic functions. Exponential functions are also periodic, having an imaginary period, and the elliptic functions have not only a real but an imaginary period, and are hence called doubly periodic. --
Periodic law (Chem.), the generalization that the properties of the chemical elements are periodic functions of their atomic weights. “In other words, if the elements are grouped in the order of their atomic weights, it will be found that nearly the same properties recur periodically throughout the entire series.” The following tabular arrangement of the atomic weights shows the regular recurrence of groups (under I., II., III., IV., etc.), each consisting of members of the same natural family. The gaps in the table indicate the probable existence of unknown elements. --
Periodic table,
Periodic table of the elements (Chem.), A tabular arrangement of the chemical elements, illustrating the periodic law, described above. [ 1913 Webster ] ☞Note: A modern version of the periodic table can be found at: https://iupac.org/what-we-do/periodic-table-of-elements/ [ PJC ] TABLE OF THE PERIODIC LAW OF THE CHEMICAL ELEMENTS(The vertical columns contain the periodic groups)Series1{ 2{ 3{ 4{ 5{ 6{ 7{ 8{ 9{ 10{ 11{ 12{

-------------------------------------------------------------- |I. II. III. IV. V. VI. VII. VIII. | RH4 RH3 RH3 RH  |R2O RO R3O3 RO2 R2O5 RO3 R2O7 RO4  --------------------------------------------------------------

H
1
Li
7
Na
23
K
39
(Cu)
63
Rb
85.2
(Ag)
(108)
Cs
133
(-)
(-)
(Au)
(197)
-----------------------------------------------------------------
[ 1913 Webster ] ☞ A similar relation had been enunciated in a crude way by Newlands; but the law in its effective form was developed and elaborated by Mendelejeff, whence it is sometimes called Mendelejeff's law. Important extensions of it were also made by L. Meyer. By this means Mendelejeff predicted with remarkable accuracy the hypothetical elements ekaboron, ekaluminium, and ekasilicon, afterwards discovered and named respectively scandium, gallium, and germanium. [ 1913 Webster ] --
Periodic star (Astron.), a variable star whose changes of brightness recur at fixed periods. --
Periodic time of a heavenly body (Astron.), the time of a complete revolution of the body about the sun, or of a satellite about its primary. [ 1913 Webster ]

n. A magazine or other publication which appears at stated or regular intervals. [ 1913 Webster ]

n. One who publishes, or writes for, a periodical. [ 1913 Webster ]

adv. In a periodical{ 4 } manner; as, flooding occurs periodically in the valley. [ 1913 Webster ]

n. Periodicity. [ 1913 Webster ]

n.; pl. Periodicities [ Cf. F. périodicité. ] The quality or state of being periodical, or regularly recurrent; as, the periodicity in the vital phenomena of plants. Henfrey. [ 1913 Webster ]

n. [ Pref. per- + iodide. ] An iodide containing a higher proportion of iodine than any other iodide of the same substance or series. [ 1913 Webster ]

a. [ Pref. peri- + Gr. 'odoy`s, 'odo`ntos, tooth. ] (Anat.) Surrounding the teeth. [ 1913 Webster ]

n. (Med.) A disease that attacks the gum and bone around the teeth.
Syn. -- periodontal disease. [ WordNet 1.5 ]

n. [ Period + -scope. ] (Med.) A table or other means for calculating the periodical functions of women. Dunglison. [ 1913 Webster ]

[ So called from Salina, a town in New York. ] (Geol.) The period in which the American Upper Silurian system, containing the brine-producing rocks of central New York, was formed. See the Chart of Geology. [ 1913 Webster ]

(Geol.) A subdivision in the lower Silurian system of America; -- so named from Trenton Falls, in New York. The rocks are mostly limestones, and the period is divided into the Trenton, Utica, and Cincinnati epochs. See the Chart of Geology. [ 1913 Webster ]