In a comment to this post, "A trilingual, biscriptal note (with emoji)" (2/5/17), liuyao remarked,
Interesting that 愛 to mean (romantic) love might be a modern invention. A search in Dream of the Red Chamber (which is regarded as Beijing Mandarin in 18th century) reveals that all instances of it are in fact "to like" (something or someone). 愛吃的 = (what he) likes to eat; 不愛唸書 = doesn't like to read books/study.
liuyao's observation is so noteworthy that I promised to write a separate post on ài 愛 — herewith I am delivering on that promise.
The word that liuyao is talking about is ài 愛 / 爱 (as critics of simplified characters never tire of pointing out, the simplified form lacks a "heart" [xīn 心] at the center). Nowadays, the first English word that we think of when we see this character is "love", but that's not what it always meant, and it has many other connotations even in today's world: "passion; affection; like; cherish; treasure; hold dear; delight in; be fond of; take good care of; be enamored of; be keen on; be apt to; be in the habit of").
Here are the definitions for ài 愛 in Paul Kroll, ed., A Student's Dictionary of Classical and Medieval Chinese (Leiden: Brill, 2015), p. 1a:
1. be partial to.
a. be fond of, care for; be attached to, cherish, love (ant. 惡 wù, abhor; 憎 zēng, detest).
b. affection, kindness.
c. dear to one; admirable.
2. to pity, sympathize with.
3. be overly partial, jealous of; to stint, begrudge, be loath to part with.
4. (med.) frequently, regularly.
a. easily; prone to; with pleasure.
I recall that in the study of Literary Sinitic / Classical Chinese (LS / CC) during graduate school, one of the strongest senses I acquired for ài 愛 was "stint; (be)grudge".
In Axel Schuessler's A Dictionary of Early Zhou Chinese (Honolulu: University of Hawaii Press, 1987), p. 2 ab, he gives the following definitions: "to hold dear, to love, to grudge" (that would be for roughly the first half of the first millennium BC).
I would not want to make the claim that ài 愛 never referred to romantic love in premodern times. That is evident from the eighth among the dozen definitions of the character in Hànyǔ dà cídiǎn 漢語大詞典 (Unabridged Dictionary of Sinitic), pp. 631b-632a, and from the pages of compounds into which it enters (pp. 632a-637a). We also know from literary works throughout the ages that romantic love most certainly existed before modern times. Here I will mention only Chánghèngē 長恨歌 ("Song of Everlasting Sorrow / Regret") by Bo Juyi (772-846), which has been masterfully translated by Paul Kroll and is readily available in Victor H. Mair, ed., Columbia Anthology of Traditional Chinese Literature (New York: Columbia University Press, 1994), pp. 478-485. The character ài 愛 does occur in "Song of Everlasting Sorrow / Regret" (twice), but only in combination with other characters:
ēn'ài 恩愛 ("affection between a couple")
chǒng'ài 寵愛 ("dote on; favor; make a pet of")
Still, I think that liuyao was onto something when he noted that ài 愛 in Dream of the Red Chamber meant "like", not "love". I will illustrate this special attitude toward romantic love and its expression with the word ài 愛 from my own life experience.
My wife — following her mother — adhered to traditional Chinese norms, values, and customs. They were innate; she couldn't willingly act any other way, and it made her feel very uncomfortable to be forced by circumstances to do so.
Li-ching didn't like to say or hear others say "I'm sorry" and "Thank you". She thought those were superficial Western forms of etiquette (cf. Mary S. Erbaugh, "China expands its courtesy: Saying 'Hello' to Strangers," The Journal of Asian Studies, 67.2 [May, 2008[, 621-652).
Above all, she never once said to me "Wǒ ài nǐ 我愛你" ("I love you") and she would have found it "disgusting / nauseating" (ròumá 肉麻) for me to say such things to her. She really did not like to hear them.
We were married for 41 years; we deeply cherished each other and had tremendous respect for one another; but throughout our marriage we never said those three words to each other.