Any of a variety of substances having a structure containing a beta-lactam ring fused to a thiirane ring, to which a carboxyl group is attached, but most commonly interpreted as benzyl penicillin. They are notable as powerful antibacterial agents of relatively low toxicity which have found extensive use in medicine for treating bacterial infections. They are categorized as one of the classes of beta-lactam antibiotic. They are produced naturally by some fungi and bacteria, and industrial production processes almost invariably start from some form of the penicillin nucleus produced by fermentation of microorganisms. The fermentation products are then chemically modified to produce derivatives of enhanced potency, safety, or antibacterial spectrum. The first penicillin to see extensive use clinically (during World War II) was penicillin G, also called benzypenicillin, and commonly simply /penicillin/.

An enzyme which destroys the antibacterial activity of penicillin by hydrolyzing the amide bond in the beta-lactam ring. Many penicillinases are known, and are produced by a wide variety of bacteria. The production of penicillinase is one of the mechanisms by which bacteria may become resistant to penicillins. Penicillinase production in various bacterial species may be induced, i.e., it may occur only when stimulated by the presence of penicillin in the culture medium, or it may be constitutive, i.e., it may occur whenever the cells are producing protein. Molecular weights of the various penicillinases tend to cluster near 50,000.

A portion of land nearly surrounded by water, and connected with a larger body by a neck, or isthmus.

Of or pertaining to a peninsula; as, a peninsular form; peninsular people; the peninsular war.

To form into a peninsula.

The erectile external sexual organ of males, used in copulation, and in mammals, also for urination.

The quality or condition of being penitent; the disposition of a penitent; sorrow for sins or faults; repentance; contrition.

A priest who heard confession and enjoined penance in extraordinary cases.

Penitence.

One who repents of sin; one sorrowful on account of his transgressions.

A book formerly used by priests hearing confessions, containing rules for the imposition of penances; -- called also penitential book.

In a penitential manner.

One who prescribes the rules and measures of penance.

The office or condition of a penitentiary of the papal court.

In a penitent manner.

A minnow. See Pink, n., 4.

A small pocketknife; formerly, a knife used for making and mending quill pens.

A small flashlight resembling a fountain pen, often having a clip to permit firm attachment to a pocket.

One who uses the pen; a writer; esp., one skilled in the use of the pen; a calligrapher; a writing master.

The use of the pen in writing; the art of writing; style or manner of writing; chirography; as, good or bad penmanship.

A perfect, or normal, feather.

Like or pertaining to a normal feather.

A bunch of feathers; a plume.

Variegated; striped.

Feathery covering; plumage.

A small flag; a pennon. The narrow pennant, or long pennant (called also whip or coach whip) is a long, narrow piece of bunting, carried at the masthead of a government vessel in commission. The board pennant is an oblong, nearly square flag, carried at the masthead of a commodore's vessel. A rope or strap to which a purchase is hooked.

Winged; plume-shaped.

Any one of numerous species of Pennatula, Pteroides, and allied genera of Alcyonaria, having a featherlike form; a sea-pen. The zooids are situated along one edge of the side branches.

A division of alcyonoid corals, including the seapens and related kinds. They are able to move about by means of the hollow muscular peduncle, which also serves to support them upright in the mud. See Pennatula, and Illust. under Alcyonaria.

Winged; having plumes.

One who pens; a writer.

Having the form of a feather or plume.

Bearing feathers or quills.

Destitute of money; impecunious; poor.

Pinnately veined or nerved.

Strong of wing; strong on the wing.

A pennant; a flag or streamer.

A small pennon borne on a lance. See Pencel.

The geological period from 280 million to 310 million years ago; -- it was characterized by a warm climate and abundance of swampy land.

Worth or costing one penny; as, penny candy.

One who furnishes matter to public journals at so much a line; a poor writer for hire; a hack writer.

Scrimping; reluctant to spend money; stingy; miserly; same as cheesparing.

Thrifty in small matters only. Used mostly in the phrase penny-wise and pound foolish.

Any of several plants of the genus Thlaspi; see penny cress.

An aromatic herb (Mentha Pulegium) of Europe; also, a North American plant (Hedeoma pulegioides) resembling it in flavor.

A troy weight containing twenty-four grains, or the twentieth part of a troy ounce; 1.555 grams; as, a pennyweight of gold or of arsenic. It is abbreviated dwt or pwt. It was anciently the weight of a silver penny, whence the name.

A European trailing herb (Linaria Cymbalaria) with roundish, reniform leaves. It is often cultivated in hanging baskets.

A penny's worth; as much as may be bought for a penny.

See Pend.

Of or pertaining to penology.

One versed in, or a student of, penology.

The science or art of punishment.

A rack for pens not in use.

pl. of Penny; pence.

Pensive.

A pencel.

Held aloft.

Hanging; suspended; pendent; pendulous.

State or quality of being pensile; pendulousness.

To grant a pension to; to pay a regular stipend to; in consideration of service already performed; -- sometimes followed by off; as, to pension off a servant.

One who receives a pension; a pensioner.

One in receipt of a pension; hence, figuratively, a dependent.

Thoughtful, sober, or sad; employed in serious reflection; given to, or favorable to, earnest or melancholy musing.

Made pensive.

In a pensive manner.

The state of being pensive; serious thoughtfulness; seriousness.

A large genus of subshrubs or herbs having showy blue or purple or red or yellow or white flowers; found mostly in Western North America.

A close conduit or pipe for conducting water, as, to a water wheel, or for emptying a pond, or for domestic uses.

Penned or shut up; confined; -- often with up.

Same as penta-; -- used as a combining form before vowels, as in pentoxide.

A combining form denoting five; as, pentacapsular; pentagon.

Capable of uniting with five molecules of a monacid base; having five acid hydrogen atoms capable of substitution by a basic radical; -- said of certain acids.

Having five capsules.

A dry fruit composed of five carpels, which are covered by an epigynous calyx and separate at maturity.

A chloride having five atoms of chlorine in each molecule; as, phosphorus pentachloride.

An ancient instrument of music with five strings.

Capable of neutralizing, or combining with, five molecules of a monobasic acid; having five hydrogen atoms capable of substitution by acid residues; -- said of certain complex bases.

A five-pointed star, also called a pentagram or pentalpha. See illustr. under pentalpha. Sometimes referring to a similar figure, such as the figure composed of two equilateral triangles intersecting so as to form a six-pointed star. It was used in early ornamental art, and also with superstitious import by the astrologers and mystics of the Middle Ages. The six-pointed star is more comonly called a hexagram, or called Solomon's seal; it resembles the star of David (Magen David)

Composed of five united carpels with one seed in each, as certain fruits.

See Penteconter.

A red and purple pigment found in certain crinoids of the genus Pentacrinus.

Any species of Pentacrinus.

An immature comatula when it is still attached by a stem, and thus resembles a Pentacrinus.

A genus of large, stalked crinoids, of which several species occur in deep water among the West Indies and elsewhere.

A solid having five summits or angular points.

A set of verses so disposed that the name forming the subject of the acrostic occurs five times -- the whole set of verses being divided into five different parts from top to bottom.

Having the valence of a pentad.

Having five digits to the hand or foot.

Having the form of, or a structure modified from, a pentadactyl limb.

A hydrocarbon of the paraffin series, (C15H32) found in petroleum, tar oil, etc., and obtained as a colorless liquid; -- so called from the fifteen carbon atoms in the molecule.

Of, pertaining to, or derived from, pentadecane, or designating an acid related to it.

Same as Quindecylic-- = pentadecyl? -->.

Having the stamens arranged in five clusters, those of each cluster having their filaments more or less united, as the flowers of the linden.

Divided or cleft into five parts.

A work in five different tongues.

A plane figure having five angles, and, consequently, five sides; any figure having five angles.

Having five corners or angles.

In the form of a pentagon; with five angles.

Pentagonal.

A pentacle or a pentalpha.

Pantographic. See Pantograph.

A Linn/an order of plants, having five styles or pistils.

Of or pertaining to plants of the order Pentagyna; having five styles.

Having five sides; as, a pentahedral figure.

Pentahedral.

A solid figure having five sides.

Pentahedral.

A peculiar insectivore (Ptilocercus Lowii) of Borneo; -- so called from its very long, quill-shaped tail, which is scaly at the base and plumose at the tip.

A five-pointed star, resembling five alphas joined at their bases; -- used as a symbol.

An extensive division of Coleoptera, including those that normally have five-jointed tarsi. It embraces about half of all the known species of the Coleoptera.

One of the Pentamera.

Divided into, or consisting of, five parts; also, arranged in sets, with five parts in each set, as a flower with five sepals, five petals, five, or twice five, stamens, and five pistils.

A genus of extinct Paleozoic brachiopods, often very abundant in the Upper Silurian.

Having five metrical feet.

A hypothetical hydrocarbon, C5H10, metameric with the amylenes, and the nucleus of a large number of derivatives; -- so named because regarded as composed of five methylene residues. Cf. Trimethylene, and Tetramethylene.

A Linn/an class of plants having five separate stamens.

Of or pertaining to the class Pentadria; having five stamens.

Any one of the three metameric hydrocarbons, C5H12, of the methane or paraffin series. They are colorless, volatile liquids, two of which occur in petroleum. So called because of the five carbon atoms in the molecule.

A pentagon.

Having five corners or angles.