Let's break down the question and find the most appropriate antonym for the word RESPONSIBLE.

Understanding Antonyms and RESPONSIBLE

An antonym is a word that means the opposite of another word. The word RESPONSIBLE generally means:

• Being the cause of something, or being answerable for something.
• Having control or authority over something or someone.
• Being able to be trusted or relied on; conscientious.

We are looking for a word that means the opposite of these senses, particularly the sense of being trustworthy, reliable, or answerable for one's actions.

Analyzing the Antonym Options

Let's look at the given options and evaluate which one serves as the most appropriate antonym for RESPONSIBLE.

1. irresponsible: The prefix 'ir-' is often used to form antonyms, especially before words starting with 'r' (like 'regular' → 'irregular'). Irresponsible means not showing a proper sense of responsibility; careless or unreliable. This aligns perfectly with the opposite meaning of RESPONSIBLE.

2. disresponsible: The prefix 'dis-' is also used to indicate the opposite or absence of something (like 'agree' → 'disagree'). However, 'disresponsible' is not a standard or commonly accepted word in English. While 'dis-' can negate, it doesn't typically combine with 'responsible'.

3. unresponsible: The prefix 'un-' is another very common way to form antonyms (like 'happy' → 'unhappy'). While 'un-' can negate 'responsible', 'irresponsible' is the standard and widely used antonym in English. 'Unresponsible' exists but is far less common and often considered non-standard compared to 'irresponsible'.

4. illresponsible: The prefix 'ill-' can sometimes mean 'badly' or 'not' (like 'ill-advised'). However, 'illresponsible' is not a recognised word in standard English vocabulary. It does not function as an antonym for RESPONSIBLE.

Identifying the Correct Antonym

Comparing the options, irresponsible is the standard, widely accepted, and most appropriate antonym for RESPONSIBLE. It directly expresses the opposite state of not being responsible or lacking responsibility.

Revision Table: Antonyms of RESPONSIBLE

Additional Information on Negative Prefixes

English uses several prefixes to create antonyms or indicate the opposite meaning. Some common ones include:

• un-: unhappy, unclear, unbelievable
• in-/im-/il-/ir-: These are forms of the same prefix 'in-'.
  • in-: invisible, inappropriate
  • im-: used before 'm' or 'p' (impossible, impatient)
  • il-: used before 'l' (illegal, illogical)
  • ir-: used before 'r' (irregular, irrelevant, irresponsible)
• dis-: dishonest, disobey, disapprove
• a-/an-: used with Greek roots (apolitical, amoral, anaerobic)
• non-: non-fiction, non-essential

The choice of prefix often depends on the historical origin of the word and is not always predictable. For 'responsible', the standard negative prefix is 'ir-'.