How would you explain what it means to think? This act, though central to our very humanity, is an incredibly abstract process. Behind many of our thinking words, however, are some concrete Latin etymologies, and they show how we like to understand our mental activity through very physical metaphors.

1. PONDER

The origin of ponder is the Latin pondus, “weight,” used even in Ancient Rome as a metaphor for something of importance and influence. Pondus is related to the verb pendere, “to weigh,” which is why a pensive thinker really seems weighed down.

2. DELIBERATE

The metaphor of thought as weighing different matters appears in deliberate too. The ultimate root of deliberate is the Latin libra, “a pair of scales” or “balance.” A deliberate action, then, is one well weighed before undertaken.

3. CONCENTRATE

When we concentrate, we are bringing our mental efforts towards a “common center,” as the verb joins Latin’s cum (together) and centrum (center).

4. FOCUS

The central place in many homes was once the hearth or fireplace, called focus in Latin. Mathematicians and scientists used focus for a point where various phenomena (e.g., rays of light) converge, an idea later extended to thinking.

5. RUMINATE

When you ruminate, you are literally (or figuratively) chewing on something. The verb derives from Latin’s ruminare, “to chew cud,” which is ultimately why strong-stomached mammals from cows to wildebeests are known as ruminants.

6. MUSE

While the classical Muses may have caused poets to muse, the two muse words are etymologically unrelated. The absorbed-in-thought muse comes from an Old French word mus, referring to a muzzle. As the theory goes, a dog sticks its snout into the air to sniff about, to muse, for a scent. Late Latin picked up this mus as musare, “to stare” or “waste time,” which helped make the word’s way into English.

7. CONSIDER

Our noses are also skyward when we consider. According to some etymologists, consider fuses Latin’s cum (together) and sidus (constellation). The idea, here, is of an astrologist divining human affairs from the stars.

8. CONTEMPLATE

Ancient astrologists weren’t the only ones looking for answers in the sky. In Ancient Rome, augurs tried to predict the future in various natural events, especially from the flight of birds. To do so, they would mark out a special space, called a templum, with a staff to observe the sky—hence the Latin verb contemplari, “to gaze attentively.” Templum also gives English its sacred temples.

9. COMPUTE

Centuries before laptops, compute simply referred to calculating. Its root verb, the Latin computare, features that same cum (together) and putare (to think). In a much older Latin, putare actually meant “to prune,” this act of trimming back likened to “clearing up,” thus counting, final amounts. Impute, repute, and putative also feature the root putare.

10. REFLECT

Reflect’s Latin root, reflectere, involved the physical act of bending or turning back. (Re- means “back,” and flectere means “turn” or "bend,” also showing up in words like deflect, flex, and inflect.) In the late 16th century, English turned this reflect into “turning one’s thoughts back on the past.”

11. SPECULATE

Mirrors reflect our images back to us—and in Ancient Rome, the word for a mirror was speculum. This speculum, as with speculate, goes back to the Latin specere, “to see,” making speculation an act of looking more deeply at some phenomenon.

12. CONJECTURE

To conjecture, in Latin, literally means “to throw together” various bits of facts and information in coming to an explanation. Forms of its base verb, iacere, also appear in eject, interject, reject, with different prefixes specifying in what direction, exactly, something is being thrown.

13. COGITATE

To cogitate is also a kind of “tossing about” in the mind. The verb derives from the Latin cogitare, blending co- (a form of cum) and agitare (to put into motion), source of agitate.

14. MEDITATE

Deep meditation is good for the body and soul—and making a careful decision, if we look to its etymology. The base of meditate, from Latin’s meditari, is an Indo-European root med-, “to take appropriate measures,” related to me-, “to measure.”

15. SAPIENS

Anthropologists call us, modern humans, homo sapiens, or “wise person.” But sapiens (“wise”) comes from a base verb, sapere, literally meaning “to taste.” For Julius Caesar, apparently, in tasting there was sense, discrimination, understanding, and, ultimately, wisdom.