A common challenge among new cuers is deciding which handshape to use for words containing the digraph "th." In English, there are several different building blocks (phonemes) that can be represented by the letters "th."
The voiceless "th" is found in words like thief, throw, and both. In the International Phonetic Alphabet (IPA) is is represented by the theta: θ. It is also sometimes simply represented by lowercase th. In speech production, it is considered a voiceless interdental fricative – meaning that the tongue is placed between the teeth, the vocal cords do not vibrate, and that it is a noisy, turbulent sound made by a narrow constriction in the mouth.
both, cloth, death, eighth, fifth, fourth, ninth, north, south, teeth, tenth, thank, think, thing, third, thich, thought, thread, threw, through, thumb, threat, truth, with
anthem, athlete, author, bathtub, Catholic, faithful, hundredth, nothing, python, something, thirty, thunder, threatening, toothbrush
Athena, Anthony, catheter, Cynthia
authority, forsythia
anthropology
The voiced "th" is found in words like Unknown dictionary link {{those|ðoʊˈz/|those}}, brother, and worthy. In the International Phonetic Alphabet (IPA) is is represented by the eth: ð. It is also sometimes represented by tH (lowercase t and uppercase H), th (italicized th) or th (underlined th) and TH (upercase t and h), as well as combinations of those variations. In speech production, it is considered a voiced interdental fricative. It is produced nearly identically to the /θththθththθthth/ above, except with the addition of vocal cord vibration.
than, that, the, them, there, these, they, this, those, though,
bother, clothing, breathing, either, farther, father, further, leather, gather, northern, rhythm, weather
gathering
The letters "th" can represent other phonemes as well. They can less commonly (but more accurately) stand for the phonemes /t/ and /h/ as in boathouse. They can also simply represent the phoneme /ttttttttt/ as in Thai, Thomas, thyme,
While hearing, native English speakers generally do not confuse the different pronunciations of "th" while speaking, they do have difficulty consciously perceiving which they are targetting in order to assign a cue handshape. So while they can say the right sound, they may not be sure which they are saying in a given word. These stduents are encouraged to feel their vocal cords and assess the "breathiness" of their production to help them decide which handshape to use.