duplicate

The correct character is “複.” The word “複雑” (complex) expresses that many things overlap and the structure is intricate. “複” means overlapping or more than one, and it’s used in words like “複数” (multiple) and “複製” (replication). On the other hand, “復” means to return to the original state or to repeat, and appears in words like “復習” (review) and “復活” (revival).

candidate

“Kikō” refers to the long-term conditions of weather, temperature, humidity, and so on in a particular region or place, and it is written as 気候. In this case, the character for “kō” is 候. 候 also carries meanings such as “season” or “time of year,” and is used in words like 天候 (weather) and 気候 (climate). By contrast, 侯 is a different character used to indicate a rank or title, such as a noble or official position.

loss; mistake; fail; to lose (as a prefix, e.g., 失礼 = rudeness). Context is needed for a precise translation of the single character 失.

The correct kanji used for the “shitsu” in “shippai” is 失. 失 means “to lose” or “to miss,” and 失敗 (shippai) is used when you don’t achieve the desired result or when you make a mistake. On the other hand, 矢 is read as ya and means “arrow,” as in bow and arrow, and it has a completely different meaning and usage. They may look somewhat similar, but their uses are very different, so be careful not to mix them up.

product; sum; volume; pile; accumulation (context-dependent). Most commonly, in math, 積 = product.

The correct character is “積.” In mathematics, values obtained by multiplication—such as the area of a triangle or volume—use the character “積.” “積” carries the meanings “to pile up” and “the result of multiplication,” whereas “績,” as in “実績” (achievements) and “成績” (grades), refers to the results or outcomes of effort.

loan; lending; lease; to lend

“貸” is used with the meaning “to temporarily entrust something like an item or money to someone else.” In contrast, “貨” refers to money (currency) or goods in general, such as property or merchandise. In the present sentence, you are temporarily giving a paperback book to a friend—in other words, “lending” it—so the correct kanji is “貸.”

Entry

“Writing ‘niki’ as a memory of a trip” means writing down the events and feelings you experienced during your travels—in other words, keeping a “diary.” The correct kanji used here is 記. 記 means “to record” or “to write down,” and appears in words like 記録 (record) and 記念 (commemoration). By contrast, 紀 carries meanings such as “era” or “rules,” and is used in words like 紀元 (era/Anno Domini) and 世紀 (century).

govern; cure; heal; reign; rule; calm

In the sense of returning an illness or injury to its original healthy state, we use 治. 治 is a character often used in medical and health contexts. On the other hand, 冶, which can also be read as ya, is used in meanings related to manufacturing and mining/industry, such as in 冶金 (metallurgy), which refers to melting metal to shape it.