as 'c' rough breathings as 'h' both and as 'i' These conventions, which originally reflected pronunciation, have carried over into English and other languages with historical orthography, like French. They make it possible to recognize words of Greek origin, and give hints as to their pronunciation and inflection. The romanization of some digraphs is rendered in various ways in English. The diphthongs and may be spelled in three different ways in English: the Latinate digraphs ae and oe; the ligatures æ and œ; and the simple letter e. The ligatures have largely fallen out of use worldwide; the digraphs are uncommon in American usage, but remain common in British usage. The spelling depends mostly on the variety of English, not on the particular word. Examples include: encyclopaedia / encyclopædia / encyclopedia; haemoglobin / hæmoglobin / hemoglobin; and oedema / œdema / edema. Some words are almost always written with the digraph or ligature: amoeba / amœba, rarely ameba; Oedipus / Œdipus, rarely Edipus; others are almost always written with the single letter: sphære and hæresie were obsolete by 1700; phænomenon by 1800; phænotype and phænol by 1930. The verbal ending is spelled -ize in American English, and -ise or -ize in British English. Since the 19th century, a few learned words were introduced using a direct transliteration of Ancient Greek and including the Greek endings, rather than the traditional Latin-based spelling: nous (νοῦς), koine (κοινή), hoi polloi (οἱ πολλοί), kudos (κύδος), moron (μωρόν), kubernetes (κυβερνήτης). For this reason, the Ancient Greek digraph is rendered differently in different words—as i, following the standard Latin form: idol < εἴδωλον; or as ei, transliterating the Greek directly: eidetic (< εἰδητικός), deixis, seismic. Most plurals of words ending in -is are -es (pronounced [iːz]), using the regular Latin plural rather than the Greek -εις: crises, analyses, bases, with only a few didactic words having English plurals in -eis: poleis, necropoleis, and acropoleis (though acropolises is by far the most common English plural). Most learned borrowings and coinages follow the Latin system, but there are some irregularities: eureka (cf. heuristic); kaleidoscope (the regular spelling would be calidoscope) kinetic (cf. cinematography); krypton (cf. cryptic); acolyte (< ; would be the etymological spelling, but , , are all found in Latin); stoichiometry (< ; regular spelling would be ). aneurysm was formerly often spelled aneurism on the assumption that it uses the usual -ism ending. Some words