too

Etymology

From Middle English to (“also, in addition to”), from Old English tō (“furthermore, also, besides”), adverbial use of preposition tō (“to, into”). The sense of "in addition, also" deriving from the original meaning of "apart, separately" (compare Old English prefix tō- (“apart”)). Doublet of to; see there for more.

adv

1. (focus) Likewise.
   The use of algorithms in policing is one example of their increasing influence on our lives. And, as their ubiquity spreads, so too does the debate around whether we should allow ourselves to become so reliant on them – and who, if anyone, is policing their use. 2013-07-26, Leo Hickman, “How algorithms rule the world”, in The Guardian Weekly, volume 189, number 7, page 26
2. (conjunctive) Also; in addition.
   There has been a cutback in federal subsidies. Rates have been increasing too.
   Hidden behind thickets of acronyms and gorse bushes of detail, a new great game is under way across the globe. Some call it geoeconomics, but it's geopolitics too. The current power play consists of an extraordinary range of countries simultaneously sitting down to negotiate big free trade and investment agreements. 2013-07-19, Timothy Garton Ash, “Where Dr Pangloss meets Machiavelli”, in The Guardian Weekly, volume 189, number 6, page 18
3. (degree) To an excessive degree; over; more than enough.
   […]purſued his vnneighbourly purpoſe in ſuch ſort: that hee being the ſtronger perſwader, and ſhe (belike) too credulous in beleeuing or elſe ouer-feeble in reſiſting, from priuate imparlance, they fell to action; and continued their cloſe fight a long while together, vnſeene and vvithout ſuſpition, no doubt to their equall ioy and contentment. 1620, Giovanni Bocaccio, translated by John Florio, The Decameron, Containing an Hundred Pleaſant Nouels: Wittily Diſcourſed, Betweene Seuen Honourable Ladies, and Three Noble Gentlemen, Isaac Iaggard, Nouell 8, The Eighth Day
   The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania.[…]It was used to make kerosene, the main fuel for artificial lighting after overfishing led to a shortage of whale blubber. Other liquids produced in the refining process, too unstable or smoky for lamplight, were burned or dumped. 2013-08-03, “Yesterday’s fuel”, in The Economist, volume 408, number 8847
4. (degree, colloquial) To a high degree, very.
   She doesn't talk too much.  I'm not too sure about this.
5. (affirmation, colloquial) Used to contradict a negative assertion.
   "You're not old enough yet." ― "I am, too!"
6. (archaic, colloquial) Used for emphasis, without reference to any previous statement.