The letter ה represents the traditional phoneme /h/ (like the sound of <h> in the English word hat). In present-day Israeli Hebrew, this phoneme is generally dropped in ordinary speech — a word such as הֵם(hém, “them”) is usually pronounced /em/, at least in everyday conversation — but the letter ה is still used where the sound /h/ would be expected, such as in loanwords where the source word has /h/.
The letter ה is also used as a silent letter (a mater lectionis) at the end of a word, to indicate the presence of a vowel that is not otherwise indicated. This vowel is usually /a/ (as in יַלְדָּה(yaldá) and סֶלָה(séla)), but often /e/ (as in אֵלֶּה(éle) and תֵּה(té)), and in a few cases /o/ (as in כֹּה(kó)). However, final vowels are not necessarily indicated by any letter at all; for example, the words לְךָ(l'khá), אָמַרְתָּ(amárta), and אֵלֶיהָ(eléha) all end with a vowel /a/ that is not indicated by a following letter. Conversely, this silent use of ה appears, in a very small number of exceptional cases, in the interior of a word, such as in יְפֵהפֶה(y'fefé).
In writing with vowels, when a letter ה representing the phoneme /h/ occurs at the end of a word, it is written with dot inside, called a mapík, to distinguish it from the silent use: לָהּ(láh), גובה \ גֹּבַהּ(góvah).
Like the letters א, ח, ע, and ר, the letter ה never takes a dagésh (that is: in traditional Hebrew, which distinguished consonant length, the phoneme /h/ never underwent gemination), and in circumstances where a dagésh would otherwise be expected, there is frequently a change in the preceding vowel. For example, the infinitive of נֶהֱרַג(neherág) is לְהֵהָרֵג(l'heiharég) rather than *לְהִהָּרֵג(l'hiharég).
Like the letters א, ח, and ע, the letter ה generally does not take a sh'vá (be it a sh'vá ná or a sh'vá nákh); rather, it takes a khatáf vowel: הֲלִיכָה(halikhá), נֶהֱרַס(neherás), צהריים \ צָהֳרָיִם(tsohoráyim). Additionally, like word-final ח and ע, a word-final non-silent ה takes a patákh g'nuvá after any vowel other than /a/: גבוה \ גָּבֹהַּ(gavóah).
Since ה is used as a silent letter at the end of a word, it also is traditionally used as a placeholder in the representation of consonantal roots that have a sort of “gap” at the end. For example, the roots of the verbs קָנָה(kaná), נִרְאָה(nir'á), הִרְשָׁה(hirshá), חיכה \ חִכָּה(khiká), and הִתְגַּלָּה(hitgalá) are ק־נ־ה(k-n-), ר־א־ה(r-'-), ר־שׁ־ה(r-sh-), ח־כ־ה(kh-k-), and ג־ל־ה(g-l-), respectively. In some forms, this “gap” becomes ת /t/ (as in קָנְתָה(kan'tá)); in others, it becomes י /j/ (as in גילוי \ גִּלּוּי(gilúi)); in others, it becomes a silent א (as in הַרְשָׁאָה(harsha'á)); and in others, it essentially disappears (as in נִרְאוֹת(nir'ót)).
For information about ה as a prefix meaning roughly “the”, marking a noun or adjective as definite, see ה־.
For information about ה prepended to the first word of a yes-or-no question, see ה־.
For information about ה as a suffix meaning roughly “-ward”, marking a noun as an adverbial destination, see ־ה.
For information about ה as a suffix meaning roughly “her”, which is one form of the third-person feminine singular personal pronoun, see ־הּ.
For information about ה as a general feminine suffix on nouns, adjectives, and verb forms, see ־ה.
For information about ה as a sort of prefix in the past tense, infinitive forms, and/or action nouns of hif'íl, huf'ál, hitpa'él, and nif'ál verbs, see Appendix:Hebrew verbs.