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Douglas Harper's Etymology Dictionary

1909, from German PH, introduced by S.P.L. Sörensen, from P, for German Potenz "potency, power" + H, symbol for the hydrogen ion that determines acidity or alkalinity.


now in English usually representing "f," originally it was the combination used by Romans to represent Greek letter phi (cognate with Sanskrit -bh-, Germanic -b-), which at first was an aspirated "p," later the same sound as German -pf-. But by 2c. B.C.E. had become a simple sound made by blowing through the lips (bilabial spirant).\n

\nRoman "f," like modern English "f," was dentilabial; by c.400, however, the sounds had become identical and in some Romanic languages (Italian, Spanish), -ph- regularly was replaced by -f-. This tendency took hold in Old French and Middle English, but with the revival of classical learning the words subsequently were altered back to -ph- (except fancy and fantastic), and due to zealousness in this some non-Greek words in -f- began to appear confusedly in -ph-, though these forms generally have not survived.


abbr. 1 (misspelling of pH English) 2 phot


In chemistry, pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the logarithm to base 10 of the molar concentration, measured in units of moles per liter, of hydrogen ions. More precisely it is the negative of the logarithm to base 10 of the activity of the hydrogen ion. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, being neither an acid nor a base. Contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively.

pH measurements are important in agronomy, medicine, biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering, chemical engineering, nutrition, water treatment and water purification, as well as many other applications.

The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. The pH of aqueous solutions can be measured with a glass electrode and a pH meter, or an indicator.

PH (disambiguation)

pH is a measure of acidity or alkalinity.

PH, ph, pH, and Ph may also refer to:

PH (complexity)

In computational complexity theory, the complexity class PH is the union of all complexity classes in the polynomial hierarchy:

PH = ⋃Δ

PH was first defined by Larry Stockmeyer. It is a special case of hierarchy of bounded alternating Turing machine. It is contained in P = P (by Toda's theorem; the class of problems that are decidable by a polynomial time Turing machine with access to a #P or equivalently PP oracle), and also in PSPACE.

PH has a simple logical characterization: it is the set of languages expressible by second-order logic.

PH contains almost all well-known complexity classes inside PSPACE; in particular, it contains P, NP, and co-NP. It even contains probabilistic classes such as BPP and RP. However, there is some evidence that BQP, the class of problems solvable in polynomial time by a quantum computer, is not contained in PH.

P = NP if and only if P = PH. This may simplify a potential proof of PNP, since it is only necessary to separate P from the more general class PH.

Usage examples of "ph".

Ingold had a way of making anything seem possible, even feasiblethat an aimless motorcycle drifter could call forth fire from darkness, or that a mild-mannered and acroPhobic Ph.

She, at least, sent substantial sums of money to Georgos through an Athens law firm, money which permitted hirn to attend Yale and obtain a Ph.

You know, you can get hypertropHy of the rumenal walls and inhibition of cellulose-digesting bacteria with a low pH?

For an excellent and comprehensive treatise on the origins of withholding see Charlotte Twight, Ph.

The rest of the tenants were investment firms, lawyers, accountants, and, on the top story, Roone Lehmann, Ph.

He was born here and, except for college and postgrad years when he was earning his Ph.

While a few hundred Wiggaz front like boyz and girlz in da hood, there are only twenty-five real black students at PHS.

In return for a temporary transfer back to Investigations Policy, say for sixty days, I will tender my resignation from the civil service for the ostensible purpose of pursuing my Ph.

It may be observed that Quenya t, p, c descend from Primitive Elvish consonants that were certainly not aspirated, for in the primitive language they contrasted with distinct aspirated sounds: primitive th, ph, kh, which later became s, f, h in Quenya.

         We may also consider the primitive aspirated consonants kh, th, ph, pronounced more or less as in as in backhand, outhouse, scrap-heap (to borrow my own examples from Lesson One).

However, following at least some consonants, the primitive aspirates kh, ph, th lost their aspiration (the h element) and became unaspirated k, p, t instead.

She trundled past Bennett into the living room and climbed up on the couch next to the gypsy mo r ph.

Standard Bushmasters had neither laser sights nor a selectable switch but the armorer, who had a Ph.

Clarence McQuade who was the team's star chess player, to blow out by his own estimate not less than twenty percent of his brain on speed, meth, "crank" in graduate school at Berkeley, researching problem in de Rham cohomology for a math Ph.

What about the Problems of a President, the Backward Passes of a Footballer, the Deferrals of a Dean, the Odd Volumes of a Librarian, the Footnotes of a Ph.