noun
cursive handwriting; connected characters; running script
Refers to writing in which characters are joined together in a flowing, cursive style, as opposed to printed or separated characters. Often used in calligraphy or informal handwriting.
祖父の手紙は続け字で書かれていて、読むのが難しい。
My grandfather's letters are written in cursive, so they are hard to read.
続け字を練習すると、筆記体のような流れる文字が書けるようになる。
Practicing connected characters lets you write flowing letters like cursive.
筆記体 refers specifically to cursive writing in the Latin alphabet, while 続け字 is used for Japanese characters written in a connected, flowing style.
草書 is a highly cursive style of Chinese/Japanese calligraphy, often abbreviated and artistic; 続け字 is a more general term for any connected handwriting, not necessarily as stylized.
Compound of 続け (continuation) + 字 (character). The exact historical derivation is uncertain, but the term straightforwardly describes characters written in a continuous, connected manner.