Quick Summary

The prefix ob-, besides meaning “against” or “towards,” can also act as an intensive prefix. An intensive prefix can effectively be translated as “thoroughly” to highlight its emphatic function. The intensive nature of the prefix ob- shows up in such words as obtuse and obdurate. An example to help remember this intensive prefix is the word obtain, for when you obtain something you “thoroughly” hold onto it.

The Intensive Prefix "Ob-"

Prefixes can emphasize roots of words to which they are attached; in this capacity they are known as intensive prefixes. Today we will explore the intensive nature of the prefix ob-, which besides meaning “against” or “towards” can also be translated as “thoroughly” when acting as an intensive.

The prefix ob- most commonly means “against,” such as in the word “obstacle,” and “towards,” as in the word “obligation.” Ob-, however, can also act as an intensive, meaning “thoroughly” or “very.” Imagine that one hot day you want to obtain a root beer, desiring to “thoroughly” hold onto that cold drink to cool off. You may find that at first obtaining such refreshment is obfuscated or “thoroughly” made dark to you, perhaps as dark as the root beer itself! You wonder at your own obtuseness or “thoroughly” dulled senses which simply cannot detect that root beer anywhere near you. Nevertheless you doggedly and stubbornly pursue onward, being obdurate or “thoroughly” hard in your unwillingness to give up. At long last, frustrated, you begin to shout obstreperously, or “thoroughly” make so much noise that everyone around you rushes off to buy you some root beer—oh how easy it was after all!

Sometimes prefixes can change spellings based upon the root they stand next to. For example, the intensive prefix ob- becomes oc- in the words occlude, occult, and occupy—imagine saying obclude, obcult, and obcupy! One day you might want to occupy a house, or “thoroughly” take it for your own. Insufficient personal finances, however, can encourage mortgage companies to occlude you from doing so, thus “thoroughly” blocking you from obtaining that house. Unscrupulous potential homeowners might resort to occultation, or “thoroughly” hiding the true state of their finances in order to obtain that home they so greatly desire!

Hopefully you have now obtained sufficient knowledge about the intensive prefix ob-, which will now no longer occlude your ability to understand words with that prefix in them!

  1. obstacle: that which stands “against”
  2. obligation: that which ties “towards” you
  3. obtain: “thoroughly” hold onto
  4. obfuscate: “thoroughly” darken
  5. obtuse: of being “thoroughly” mentally dull
  6. obdurate: “thoroughly” hard, and so stubborn
  7. obstreperous: “thoroughly” make noise
  8. occupy: “thoroughly” take
  9. occlude: “thoroughly” block
  10. occultation: the process of “thoroughly” hiding


  • obtuse

    Someone is obtuse when they are slow to understand things; someone can choose to be obtuse when they deliberately do not try to figure things out.

  • obstreperous

    Someone who is obstreperous is noisy, unruly, and difficult to control.

  • obfuscate

    To obfuscate something is to make it deliberately unclear, confusing, and difficult to understand.

  • obdurate

    Someone who is obdurate is stubborn, unreasonable, or uncontrollable; hence, they simply refuse to change their behavior, actions, or beliefs to fit any situation whatsoever.

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