Difference between Ponder and Speculate

PONDER vs SPECULATE: NOUN

Invest at a risk
To believe especially on uncertain or tentative grounds
Talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion
To think, meditate or reflect on a subject; to deliberate or cogitate
To make an inference based on inconclusive evidence; to surmise or conjecture
To make a risky trade in the hope of making a profit; to venture or gamble
Reflect deeply on a subject

To engage in a course of reasoning often based on inconclusive evidence; conjecture or theorize.
To engage in the buying or selling of a commodity with an element of risk on the chance of profit.
To assume to be true without conclusive evidence.
To consider by turning a subject in the mind, and viewing it in its different aspects and relations; to meditate; to contemplate; to theorize
To view subjects from certain premises given or assumed, and infer conclusions respecting them a priori.
To purchase with the expectation of a contingent advance in value, and a consequent sale at a profit; -- often, in a somewhat depreciative sense, of unsound or hazardous transactions.

To weigh in the mind; to view with deliberation; to examine carefully; to consider attentively.
To weigh.

To think; muse; reflect; deliberate: with on or over: as, to ponder over what one has heard.
Synonyms To consider, reflect upon, etc. See list under contemplate.
To weigh carefully in the mind; consider carefully; think about; reflect upon.
I. To weigh.

To invest money for profit upon an uncertainty; take the risk of loss in view of possible gain; make a purchase or purchases, as of something liable to sudden fluctuations in price or to rapid deterioration, on the chance of selling at a large advance: as, to speculate in stocks.
To take a discursive view of a subject or subjects; note diverse aspects, relations, or probabilities; meditate; conjecture: often implying absence of definite method or result.
To pursue truth by thinking, as by mathematical reasoning, by logical analysis, or by the review of data already collected.
To take a discriminating view of; consider attentively; speculate upon; examine; inspect: as, to speculate the nature of a thing.
To view as from a watch-tower or observatory; observe.

Explore, Examine, Rethink, Consider, Wonder, Chew over, Mull over, Think over, Reflect, Muse, Meditate, Speculate, Ruminate, Mull, Contemplate

Mull over, Hypothecate, Job, Meditate, Muse, Reflect, Suppose, Ruminate, Mull, Contemplate, Ponder, Theorise, Conjecture, Hypothesize, Theorize

Think, Weigh, Explore, Examine, Consider, Wonder, Think over, Chew over, Reflect, Muse, Meditate, Speculate, Ruminate, Mull, Contemplate

Guess, Believe, Think over, Chew over, Job, Meditate, Muse, Reflect, Suppose, Ruminate, Mull, Contemplate, Ponder, Theorise, Conjecture

Stop for a second and ponder this question.
Ponder on this tonight as you sleep, muah.
Pursuing this question, people might ponder these thoughts.
Ponder, Sisters, Francine, Mary Louise and Jo Nell.
He gave the people a puzzle to ponder.
Congress should ponder in designing policy on thisscore.
But something to ponder for a future article.
Give them time to ponder your brilliant message.
Analysts and politicians alike ponder, what went wrong?
Where we ponder the different types of mobile devices we can buy, regions in Africa and Asia ponder where their next meal will come.