Definition of "Sinae"
Sinae
proper noun
(historical) Synonym of Chinese or Southern Chinese, chiefly in the context of ancient Greco-Roman knowledge of China.
Quotations
... the outmoſt people to the eaſt, next the Sinus Magnus, and inclining to the ſouth, not to be blended with the Chineſe... Beyond the Sinae to the eaſt, and ſouth was a terra incognita... Iſ. Voſſius takes the Sinae to be the Siameſe; becauſe at this day the appellation Sinae is unknown aamong them; an argument which de Pinedo on Stephanus treats as trifling.
1773, Alexander MacBean, A Dictionary of Ancient Geography..., s.v. "Sinae"
Exactly which term, "Sinae" or "Serica", equates to the modern China is a bit muddled. Sinae could refer to eastern peninsular Southeast Asia or southern China or both whereas Serica could refer to northern China or Xinjiang and eastern Central Asia or both.
2008, Richard L. Smith, Premodern Trade in World History, p. 111