The basis for thePhilippine national language is Tagalog, which had primarilybeen spoken only in Manila and the surrounding provinces when the Commonwealthconstitution was drawn up in the 1930s. That constitution provided for anational language, but did not specifically designate it as Tagalog because ofobjections raised by representatives from other parts of the country whereTagalog was not spoken. It merely stated that a national language acceptable tothe entire populace (and ideally incorporating elements from the diverselanguages spoken throughout the islands) would be a future goal. Tagalog, ofcourse, by virtue of being the lingua franca of those wholived in or near the government capital, was the predominant candidate.
By the time work on a new constitution began in the early 1970s, more than halfthe Philippine citizenry was communicating in Tagalog on a regular basis.(Forty years earlier, it was barely 25 percent.) Spurred on by President Marcosand his dream of a "New Society," nationalist academics focused theirefforts on developing a national language — Pilipino, by that timeunderstood to be Tagalog de facto. Neologisms were introduced toenrich the vocabulary and replace words that were of foreign origin. Amuch-remembered example is "salumpuwit" (literally, "that tosupport the buttocks") for "chair" to replace the widelyadopted, Spanish-derived "silya." Such efforts to nativize thePhilippine national language were for naught, however, since words of Englishand Spanish origin had become an integral part of the language used in theeverday and intellectual discourse of Filipinos.
This reality was finally reflected in the constitution composed during theAquino presidency in the latter half of the 1980s. The national language waslabeled Filipino to acknowledge and embrace the existenceof and preference for many English- and Spanish-derived words."Western" letters such as f, j, c, x and z — sounds of which were notindigenous to the islands before the arrival of the Spaniards and the Americans— were included in the official Filipino alphabet.
The aforementioned evolution of the Philippine national language is taught aspart of the school curriculum in the Philippines, such that when youask a Filipino what the national language of the country is, the response is"Filipino." In the same way that there are English(composition, literature...) classes in American elementary, secondary andtertiary schools to teach the national language of the United States, there areFilipino classes (not Tagalog classes; Filipino literature classes, not Tagalogliterature classes) in Philippine schools.
So what is the difference between Filipino and Tagalog? Thinkof Filipino as Tagalog Plus. Filipino is inclusiveof the contributions of languages other than Tagalog. For instance, it is quiteall right to say diksyunaryo (fromthe Spanish diccionario) in Filipino, whereas a Tagalog purist (orsomeone stuck in the "Pilipino" era) might insist on a native Tagalogword liketalatinigan. It is also morepolitically correct to refer to Filipino, not Tagalog, as the Philippinenational language. For Filipinos from other parts of the country, Tagalog isnot their first language; they learn to speak Filipino because it is constitutionallythe national language and taught in schools.
In practical terms, most people, especially Filipinos overseas who have come torealize that foreigners favor "Tagalog" to refer to the Philippinenational language, don't strictly differentiate among the words Filipino,Pilipino and Tagalog, and have learned to adapt to how Americans or Canadiansperceive the meaning of each word. That is why when you go to a bookstore inNorth America, for example, you are more likely to find a "Tagalog (or Pilipino)dictionary" than a "Filipino dictionary."
Postscript: Philippino, Philipino and other such misspellings areunacceptable and are jarring to Filipino eyes. Remember: Filipino isthe noun that refers to the Philippine national language and to the Philippinepeople (Filipinos); it is also an adjective to describe people, things and suchfrom the Philippines (the other adjective being Philippine). Thecountry itself is called thePhilippines (currently the Republic ofthe Philippines; formerly, and actually still, the Philippine Islands) inEnglish, Las Islas Filipinas or simply La/LasFilipinas in Spanish, and Pilipinas in Filipino(Tagalog).
Cultural Note: Although the word"Filipino" is acceptable in Filipino (the Philippine language), mostFilipinos will still say Pilipino when referring to a Filipinoperson while speaking in Filipino/Tagalog.
For example: "Ako ay Pilipino." ("I amFilipino.")
Why? Primarily because a "p" sound is easier for a Filipino topronounce than an "f" sound. In fact, even though the letters c, f,j, x, z, etc. have formally been included in the Philippine/Filipino alphabet, there is still anoverwhelming tendency to transliterate foreign words into native pronunciationforms.
Examples: kompyuter, kwalipikasyon, okasyon, kendi, indibidwal, sipilis...