A diphthong known as a gliding vowel, is a combination of two adjacent vowel sounds within the same syllable. Technically, a diphthong is a vowel with two different targets: that is, the tongue moves during the pronunciation of the vowel. In most varieties of English, the phrase no highway cowboys has five distinct diphthongs, one in every syllable. Diphthongs contrast with monophthongs, where the tongue or other speech organs do not move and the syllable contains only a single vowel sound. For instance, in English, the word ah is spoken as a monophthong, while the word ow is spoken as a diphthong in most varieties. Where two adjacent vowel sounds occur in different syllables—for example, in the English word re-elect—the result is described as hiatus, not as a diphthong. Diphthongs form when separate vowels are run together in rapid speech during a conversation. However, there are unitary diphthongs, as in the English examples above, which are heard by listeners as single-vowel sounds. In the International Phonetic Alphabet, monophthongs are transcribed with one symbol, as in English sun, in which ⟨ʌ⟩ represents a monophthong.

Diphthongs are transcribed with two symbols, as in English high or cow, in which ⟨aɪ⟩ and ⟨aʊ⟩ represent diphthongs. Diphthongs may be transcribed with a vowel symbol and a semivowel symbol. In the words above, the less prominent member of the diphthong can be represented with the symbols for the palatal approximant and the labiovelar approximant, with the symbols for the close vowels and, or the symbols for the near-close vowels and: Some transcriptions are broader or narrower than others. Transcribing the English diphthongs in high and cow as ⟨aj aw⟩ or ⟨ai̯ au̯⟩ is a less precise or broader transcription, since these diphthongs end in a vowel sound, more open than the semivowels or the close vowels. Transcribing the diphthongs as ⟨aɪ̯ aʊ̯⟩ is a more precise or narrower transcription, since the English diphthongs end in the near-close vowels; the non-syllabic diacritic, the inverted breve below ⟨◌̯⟩, is placed under the less prominent part of a diphthong to show that it is part of a diphthong rather than a vowel in a separate syllable:.

When there is no contrastive vowel sequence in the language, the diacritic may be omitted. Other common indications that the two sounds are not separate vowels are a superscript, ⟨aᶦ aᶷ⟩, or a tie bar, ⟨a͡ɪ a͡ʊ⟩ or ⟨a͜ɪ a͜ʊ⟩; the tie bar can be useful when it is not clear which symbol represents the syllable nucleus, or when they have equal weight. Superscripts are used when an on- or off-glide is fleeting; the period ⟨.⟩ is the opposite of the non-syllabic diacritic: it represents a syllable break. If two vowels next to each other belong to two different syllables, meaning that they do not form a diphthong, they can be transcribed with two vowel symbols with a period in between. Thus, lower can be transcribed ⟨ˈloʊ.ər⟩, with a period separating the first syllable, from the second syllable. The non-syllabic diacritic is used only when necessary, it is omitted when there is no ambiguity, as in ⟨haɪ kaʊ⟩. No words in English have the vowel sequences *, so the non-syllabic diacritic is unnecessary.

Falling diphthongs start with a vowel quality of higher prominence and end in a semivowel with less prominence, like in eye, while rising diphthongs begin with a less prominent semivowel and end with a more prominent full vowel, similar to the in yard. The less prominent component in the diphthong may be transcribed as an approximant, thus in eye and in yard. However, when the diphthong is analysed as a single phoneme, both elements are transcribed with vowel symbols. Semivowels and approximants are not equivalent in all treatments, in the English and Italian languages, among others, many phoneticians do not consider rising combinations to be diphthongs, but rather sequences of approximant and vowel. There are many languages that contrast one or more rising diphthongs with similar sequences of a glide and a vowel in their phonetic inventory. In closing diphthongs, the second element is more close than the first. Closing diphthongs tend to be falling, opening diphthongs are rising, as open vowels are more sonorous and therefore tend to be more prominent.

However, exceptions to this rule are not rare in the world's languages. In Finnish, for instance, the opening diphthongs /ie̯/ and /uo̯/ are true falling diphthongs, since they begin louder and with higher pitch and fall in prominence during the diphthong. A third, rare type of diphthong, neither opening nor closing is height-harmonic diphthongs, with both elements at the same vowel height; these occurred in Old English: beon "be" ceald "cold"A centering diphthong is one that begins with a more peripheral vowel and ends with a more central one, such as, in Received Pronunciation or and in Irish. Many centering diphthongs are opening diphthongs. Diphthongs may contrast in how far they close. For example, Samoan

Aurangzeb Chowdhury

Admiral Aurangzeb Chowdhury, NBP, OSP, BCGM, PCGM, BCGMS, psc, BN, is a four star Admiral of Bangladesh and the current Chief of Staff of the Bangladesh Navy. He held the post of Director General of the Bangladesh Coast Guard. Abu Mozaffar Mohiuddin Mohammed Aurangzeb Chowdhury was born in Chhagalnaiya Upazila of Feni District on 28 September 1959. Chowdhury was commissioned in the Executive Branch in Bangladesh Navy on 10 December 1980, he attended various courses at abroad. He has done cadet training & basic course in Germany, Surface Warfare Officer Course in USA, Instructional Technique Course at Chittagong Teacher's Training College, Gunnery Specialization Course in India, Missile Weapon System Course in China, Naval Staff Course in Germany, C++ Programming with Operating System at AUST in Dhaka, Training on Combat System in Netherlands, Ship Building Technology Course in South Korea, BA & MDS from National University and MBA from Bangladesh Open University & presently pursuing his M Phil under BUP.

He completed NDC in 2010 and Capstone Course in 2012 from National Defence College, Dhaka. He is proficient in French, he has held a number of positions in Bangladesh Navy. He was commanding Officer of the Frigate & different ships, He served as the Assistant Chief of Naval Staff and Assistant Chief of Naval Staff at Navy HQ, he served as the Commodore Commanding Chittagong, Commodore Superintendent Dockyard, Naval Secretary & Directors at NHQ, Commandant of Marine Academy, Zonal Commander of Coast Guard East Zone and Principal of Marine Fisheries Academy, Chittagong etc. In his long illustrious career he has been awarded 16 medals. Among them, notable are Bangladesh Navy Medal, Extraordinary Service Medal, Bangladesh Coast Guard Medal, President Coast Guard Medal & Bangladesh Coast Guard Medal Service, he was made the Director General Of Bangladesh Coast Guard on 15 February 2016. He took over the office as Chief of Naval Staff on 26 January 2019, he is married to gynecologist Afroza Aurangzeb.

The couple has a son and a daughter