These seem like the same thing to me. 

Tactics involves gain of material (or rarely direct mate) and positional play involves improving relative piece activity. However, when an unstoppable threat is made through quiet moves, this is often considered a tactic. 

So why isn't positional play simply considered "an extremely complex tactic" that involves so many moves that it is not calculatable, but simply an "intuitive tactic", since when it all comes down to it, everything must be justified through variations. 

After all, when you play 2.Nf3, a good positional move, the reason it's good is because in the numerous variations, you have the choice of a better evaluation at the end of some of those variations. 

Hence, the only difference between tactics and strategy I can see is the extent to which pure calculation plays a role. But I don't see anything else. 

Thoughts?

Strategy = long-term tactics. It's basically coordinating your pieces so your position will improve (better squares, less weaknesses).

spelling and meaning

Search for Miss Strategy and Miss Tactics, they are two titled players that discuss games and give advice. By the way, cool username, I know what you did there.

I thought it was always "Strategy is what you do when there aren't any tactics"? 

Tactics

A tactic is a short sequence of moves, usually involving an attack or capture, that attempts to make an immediate tangible gain. Tactics are the first thing you look for when considering any move. The common tactics have been given names to distinguish them. Some of the most common ones are:

• Forks
• Pins
• Skewers
• Discovered Attacks
• Removing the Guard

Strategy

When you aren't able to take advantage of a tactic, you turn to strategy. A strategy is a long term plan or idea. It is usually based on positional considerations, rather than attacks and captures. Some of the common positional elements that form the basis for strategy are:

• Piece Mobility
• Piece Safety
• King Safety
• Pawn Structure

Tactics and strategy are intertwined with one another. Strategic moves often have the objective of setting up future tactical maneuvers, and vise versa.

For the novice player, tactics is by far the more important consideration. Almost all games below the master level are won and lost through tactical mistakes. This thought should guide the study of the improving player. If you want to improve fast, study tactics!

Tactic = short term idea/plan

Strategy = long term idea/plan

...if you can't remember Diakonia's comprehensive definitions in relevence to chess 

Cant remember?  How can you not rem...what were we talking about?

   Strategy is 'What' you want to achieve. Say, a material advantage.

Tactics is 'How' you go about achieving that. Say, a Queen Sacrifice.

Thank you guys for the informative answers, particularly Diakonia. 

My thinking is that, computers don't know the difference between tactics and positional play/strategy; they just find good moves by calculating everything possible and evaluating with set criteria.

Tactics vs Strategy is clearly a much clearler dichotomy for any human player though, through short and long term ideas. 

it's similar to virtue & value... virtue is only a word, it becomes value when you do it

so strategy becomes tactic when you perform it

Tactics originated from tact which means manipulation of fact. Fact means reality or current reality. One can learn simple tactics very easily.There are two types of tactics-

1. Simple tactics
2. Deep tactics

Strategy means overall plan to capture grand value by positioning & controlling tactics. In chess, there are 6 types of strategies.

I like a broad and rather humorous definition:

Tactics is what is used in a game where there is something to be done, and strategy is what is used when there is nothing to be done.

I really like that definition

it's a good strategy to look out for tactics.

It's a good strategy to make tactics ever more likely.

yes, that's my favourite strategy :)

facepalm.

• "Tactics is knowing what to do when there is something to do. Strategy is knowing what to do when there is nothing to do" 
• Savielly Tartakower 
• Tactics is from the greek word "taktika", matters pertaining to arrangement, or from the greek word "taktikē" (tekhnē), (art) of deploying forces in war, both from "taktikos", of order, from "taktos", arranged, from "tassein", tag-, to arrange.
• Strategy is from  the greek word  "stratēgiā", office of a general, from "stratēgos", general; see "stratagem".

Tactics is the part of the game that you can teach a computer how to do, and strategy is everything else.