Rectangular wing - kukeiyoku

...However, since the mutual interference of pressure between the upper and lower wings results in a slight loss of lift, which is an aerodynamic disadvantage, it has rarely been used since there is no longer a structural need for a biplane.
[Taper classification]
A rectangular wing with a constant chord length is called a rectangular wing, and a trapezoidal wing whose tip is thinner than its base is called a tapered wing (Figure 6-d). Tapered wings are advantageous in making the wing structure lighter and also increase the volume of the fuel tank inside the wing, but if the tip is made too thin, tip stall becomes more likely to occur, so except for wings with a small aspect ratio, the taper ratio is usually set to 0.25 or more. …

*Some of the terminology that refers to "rectangular wing" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…しかし上下の翼の圧力の相互干渉で揚力に若干のロスがあり空力的に損なので，構造上複葉にする必要がなくなってからはほとんど使われていない。
［テーパーによる分類］
　翼弦長が一定の長方形の翼を矩形翼，付け根より翼端が細い台形の翼をテーパー翼(先細翼)と呼ぶ(図6-d)。テーパー翼は翼の構造を軽く作るのに有利で翼内の燃料タンクの容積も大きくなるが，あまり翼端を細くしすぎると翼端失速を起こしやすくなるので，アスペクト比の小さい翼を除けば，ふつうテーパー比を0.25以上としている。…

※「矩形翼」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報