The period, the present or current time, as distinguished from all
other times.
Syn. -- Time; date; epoch; era; age; duration; limit; bound; end;
conclusion; determination.
Pe"ri*od (?), v. t. To put an end to. [Obs.] Shak.
Pe"ri*od, v. i. To come to a period; to conclude. [Obs.] "You may
period upon this, that," etc. Felthman.
Per*i"o*date (?), n. (Chem.) A salt of periodic acid.
Per`i*od"ic (?), a. [Pref. per- + iodic.] (Chem.) Pertaining to,
derived from, or designating, the highest oxygen acid (HIO&?;) of
iodine.
{ Pe`ri*od"ic (?), Pe`ri*od"ic*al (?), } a. [L. periodicus, Gr. &?;:
cf. F. pÈriodique.] 1. Of or pertaining to a period or periods, or to
division by periods.
The periodicaltimes of all the satellites.
Sir J. Herschel.
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.
3. Happening, by revolution, at a stated time; returning regularly,
after a certain period of time; acting, happening, or appearing, at
fixed intervals; recurring; as, periodical epidemics.
The periodic return of a plant's flowering.
Henslow.
To influence opinion through the periodical press.
Courthope.
4. (Rhet.) Of or pertaining to a period; constituting a complete
sentence.
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 wieghts. "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.
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.
-- 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.
Pe`ri*od"ic*al, n. A magazine or other publication which appears at
stated or regular intervals.
Pe`ri*od"ic*al*ist, n. One who publishes, or writes for, a periodical.
Pe`ri*od"ic*al*ly, adv. In a periodical manner.
Pe`ri*od"ic*al*ness, n. Periodicity.
Pe`ri*o*dic"i*ty (?), n.; pl. Periodicities (#). [Cf. F. pÈriodicitÈ.]
The quality or state of being periodical, or regularly recurrent; as,
the periodicity in the vital phenomena of plants. Henfrey.
Per*i"o*dide (?), n. [Pref. per- + iodide.] An iodide containing a
higher proportion of iodine than any other iodide of the same substance
or series.
Per`i*o*don"tal (?), a. [Pref. peri- + Gr. &?;, &?;, tooth.] (Anat.)
Surrounding the teeth.
Pe`ri*od"o*scope (?), n. [Period + -scope.] (Med.) A table or other
means for calculating the periodical functions of women. Dunglison.
{ ||Per`i*ú"ci, Per`i*ú"cians, } n. pl. [NL. perioeci, fr. Gr. &?;; &?;
around + &?; house, dwelling.] Those who live on the same parallel of
latitude but on opposite meridians, so that it is noon in one place
when it is midnight in the other. Compare Antúci.
Per"i*o*ple (?), n. [F. pÈriople, from Gr. &?; about + &?; the hoof of
a horse.] (Anat.) The external smooth horny layer of the hoof of the
horse and allied animals.
Per`i*op"lic (?), a. (Anat.) Of or pertaining to the periople;
connected with the periople.
Per`i*os"te*al (?), a. (Anat.) Situated around bone; of or pertaining
to the periosteum.
||Per`i*os"te*um (?), n. [NL., fr. Gr. &?; round the bones; &?; around
||+ &?; a bone: cf. L. periosteon.] (Anat.) The membrane of fibrous
||connective tissue which closely invests all bones except at the
||articular surfaces.
||Per`i*os*ti"tis (?), n. [NL. See Periosteum, and -itis.] (Med.)
||Inflammation of the periosteum.
||Per`i*os"tra*cum (?), n.; pl. Periostraca (#). [NL., fr. Gr. &?;
||around + &?; shell of a testacean.] (Zoˆl.) A chitinous membrane
||covering the exterior of many shells; -- called also epidermis.
Per`i*o"tic (?), a. [Pref. peri- + Gr. &?;, &?;, the ear.] (Anat.)
Surrounding, or pertaining to the region surrounding, the internal ear;
as, the periotic capsule. -- n. A periotic bone.