Initial

初始

chūshǐ

(chronologically first)

最初

zuìchū

(chronologically first)

紐 /纽

niǔ

(first part of a syllable (onset))

聲母 /声母

shēngmǔ

(first part of a syllable (onset))

聲紐 /声纽

shēngniǔ

(first part of a syllable (onset))

音紐 /音纽

yīnniǔ

(first part of a syllable (onset))

首字放大

shǒuzì fàngdà

(calligraphy: distinguished initial letter)

首字母

shǒuzìmǔ

(first letter of a word)

草簽 /草签

cǎoqiān

(to sign one's initial(s))