to think; to consider; to miss; to long for; an idea; thought
思 is thinking and missing: 思考 'to think over', 思念 'to miss', 意思 'meaning'.
GF0025–2021 character list · 二级WHOLE GLYPH & STRUCTURE
ZDIC: 会意兼形声，从心、从囟、囟亦声 — the heart under the brain-pan graph 囟 (xìn), which was also the sound. The modern top is written 田.
WHOLE CHARACTER
to think; to consider; to miss; to long for; an idea; thought
思 is thinking and missing: 思考 'to think over', 思念 'to miss', 意思 'meaning'.
ZDIC: 会意兼形声，从心、从囟、囟亦声 — the heart under the brain-pan graph 囟 (xìn), which was also the sound. The modern top is written 田.
TOP: THE WRITTEN TOP, SHAPED LIKE 田
field; farmland
Standalone meaning is kept separate from its role in other characters.
In 思: top: the written top, shaped like 田 The old top was 囟 (xìn); that story is not visible in today's 田 shape.
BOTTOM: THE HEART SIDE (ZDIC: 从心)
heart; mind
Mind/feeling clue.
In 思: bottom: the heart side (ZDIC: 从心) Shown with its documented or clearly limited role.
Kept for the classical 于思 'bushy-bearded'; not a modern common reading. No learner words.
No common modern word is offered for this reading; the dictionary sense remains in Sources.
Checking for a Mandarin voice…