[9.1] How can I build hypertexts so individual words in a field can be clicked on to link to other parts of the movie?

While it isn't directly possible to define individual words in a field as buttons, it is easy to make the whole field a button and check which word was clicked in its mouseUp handler:

-- sprite script for some field called "wotsit"

on mouseUp
  -- find out the number of the word that was clicked
  put the mouseWord into wordNum
  -- discover what that word actually is
  put word wordNum of field "wotsit" into clickedWord
  -- act appropriately
  if clickedWord = "blah" then go to "info about blah"
end mouseUp

As well as the mouseWord, Director provides some other functions to determine what part of a field the mouse is over:

  the mouseChar
  the mouseItem
  the mouseLine

All of these return the number of their respective chunk in the field that the mouse is over (if it is over a field). If you wish to discover what that chunk contains, you have to get it from the field much as the mouseUp handler above does. (It is quicker not to, however. Putting the actual words in the script will make things clearer, but for optimum performance you may want to use the numbers directly.)

These functions need not be used in response to a click. You may, for example, want to hilite the item under the mouse as the user moves it around by putting something like this in your idle script:

-- very basic handler to hilite any item under the mouse
-- NB: a useable version would probably also unhilite items
-- when the mouse leaves the field

on idle
  put the mouseItem into theItem
  put the mouseCast into theField
  if theItem>0 and theField>0 then hilite item theItem of field theField
end idle

Note that if the mouse is not over a text field, or is over some inappropriate part of it like the border or scroll bars these functions return -1 (that's what the if statement is for in the above handler), but if the mouse is over empty space beyond the last chunk in the field, the functions return the number of the last chunk.