Sugar orange (English spelling)

Japanese: sugar orange（英語表記）sugarorange

…When we say orange, we usually mean this sweet orange. It can be further divided into four types: common oranges such as Valencia oranges (illustration), navel oranges, blood oranges (or pigmented oranges), and sugar oranges (or acidless oranges). (2) Sour orange C. aurantium L. (English name: sour orange) Also called bitter orange. …

From Sweet Orange

...It is cultivated in large quantities in Italy, Spain, etc. (4) Acid-free oranges Sugar oranges have the same appearance as regular oranges, but the acid content in the juice is very low (about 0.2%), so they have almost no sour taste. They are cultivated in Arab countries, etc.

*Some of the terminology that mentions "sugar orange" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…普通にオレンジというとこのスイートオレンジをさす。さらにバレンシアオレンジ（イラスト）などの普通系オレンジcommon orange，ネーブルオレンジnavel orange，血ミカンblood orange(またはpigmented orange)，無酸オレンジsugar orange(またはacidless orange)の4種に分類できる。(2)サワーオレンジC.aurantium L.(英名sour orange)　ビターオレンジbitter orangeともいわれる。…