As Thick as Thieves – Meaning, Example & Usage

The phrase thick as thieves is an 18th-century, French saying that literally describes how thieves move together like a pack at a fair, showing closeness, honor, and trusting bond among people. Originally, it was used to express the complicit, secretive, and close relationships of thieves, but today it also carries a positive meaning for friends who are incredibly, very, or almost like family. 

Understanding this idiom, its origins, meaning, and usage can help in English learning, especially when dealing with unfamiliar phrases, words, and expressions in everyday conversations or media.

In practice, saying two coworkers, friends, or other people are thick as thieves paints a picture of a strong, trusting, and special bond, where secrets are safe, support is always given, and help is freely shared. 

Using this phrase creatively in articles, literature, or conversations adds color to the language, making it easier for English speakers to tick ideas naturally, depend on each other, and learn through examples, references, or comparables that are synonymous with friendship, good, or even crime-related contexts, whether at work, outside, or together in time and activities.

What Does “As Thick as Thieves” Mean?

The phrase “as thick as thieves” is an English idiom used to describe two or more people who are extremely close, friendly, and share a strong bond. When people are “as thick as thieves,” they trust each other deeply and often act as a united team.

In simple terms, it means:

• Very close friends
  
• Inseparable companions
  
• People who share secrets and loyalty
  

Example:

• Sarah and Jane are as thick as thieves; they’ve been inseparable since kindergarten.
  

This idiom emphasizes intimacy and trust between people, often implying that they are so close that they might even share secrets or schemes.

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Origin and History of the Phrase

The expression “as thick as thieves” dates back to the early 17th century. It originally referred to criminals or thieves, highlighting how criminals work closely together, trusting each other completely. Over time, the phrase shifted from a negative criminal context to a general description of close friendship.

• Early Usage: In the 1600s, it appeared in literature describing conspiracies and secretive behavior.
  
• Modern Usage: Today, it is mostly used in a friendly context, without implying crime.
  

Fun Fact: The word “thick” in this phrase doesn’t refer to physical thickness; it means intimate or very close.

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How to Use “As Thick as Thieves” in a Sentence

Using this idiom is straightforward once you understand the pattern. Typically, it follows this structure:

• [Person A] and [Person B] are as thick as thieves.
  
• [Group of people] have been as thick as thieves since [time].
  

Examples:

• The two teammates are as thick as thieves, always supporting each other on and off the field.
  
• My cousins have been as thick as thieves since childhood.
  

You can also use it in informal conversations, workplace storytelling, and writing dialogue in stories. It adds a natural, idiomatic touch to English.

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Correct vs Incorrect Usage Examples

Understanding how to use the phrase correctly helps avoid confusion. Here’s a comparison:

Correct Usage	Incorrect Usage	Why It’s Incorrect
They are as thick as thieves and share everything.	They are thick thieves.	“Thick thieves” loses the idiomatic meaning and sounds like a description of criminals.
Jane and I have been as thick as thieves since school.	Jane and I are as thick thieves.	Missing “as … as” breaks the idiom structure.
The two sisters are as thick as thieves.	The two sisters are thick like thieves.	“Like” changes the idiom and sounds unnatural in modern English.

Tip: Always remember the exact phrase: “as thick as thieves”. Changing it makes it incorrect.

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Common Mistakes Learners Make

Many English learners misuse this phrase because it contains words with multiple meanings:

1. Dropping “as”
   
   • Incorrect: They are thick thieves.
     
   • Correct: They are as thick as thieves.
     
2. Literal Interpretation
   
   • Some learners think it refers to actual thieves.
     
   • Remember, in modern English, it describes closeness and friendship, not crime.
     
3. Overusing in formal writing
   
   • It’s idiomatic and conversational, so it may sound out of place in very formal contexts.
     
4. Confusing with other “thick” idioms
   
   • “Thick-skinned” = not easily offended
     
   • “Thick-headed” = stubborn or not smart
     
   • Don’t mix these with “as thick as thieves.”
     

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Synonyms and Alternative Phrases

If you want to vary your writing, here are some synonyms and alternatives:

Synonym/Alternative	Notes
Best friends	Simple and widely understood
Inseparable	Emphasizes being always together
Bosom buddies	Slightly old-fashioned but charming
Close-knit	Often used for families or teams
Joined at the hip	Informal, emphasizes constant togetherness
Peas in a pod	Friendly and casual, often used for similarities

Example using alternative phrases:

• They are inseparable; truly joined at the hip since college.
  

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Idioms Related to Close Friendships

Learning related idioms can expand vocabulary and make conversations richer:

• Birds of a feather flock together – People with similar interests stick together.
  
• Thick as pea soup – (Not common for friendship) Usually literal, be careful.
  
• Hand in glove – Working together closely, often professionally.
  
• Partners in crime – Similar in meaning, playful, and informal.
  

Tip: Using these idioms naturally will make ESL speakers sound more like native English speakers.

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Real-Life Situations Where You Can Use This Phrase

Here are examples of practical usage:

1. School/College:
   
   • Mark and Tom are as thick as thieves; they study and play sports together.
     
2. Workplace:
   
   • Those two colleagues are as thick as thieves, always helping each other finish projects.
     
3. Family & Relatives:
   
   • My sisters are as thick as thieves; they share secrets and support each other.
     
4. Social Media Captions:
   
   • My bestie and I, as thick as thieves forever! 💕
     

Using this idiom in everyday speech makes it more memorable and natural.

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Tips for ESL Learners to Remember the Meaning

Here are some practical tips to internalize “as thick as thieves”:

• Visualize the meaning: Imagine two people always together, sharing secrets.
  
• Remember the word pattern: as … as … is essential.
  
• Use real-life examples: Relate it to your friends or family.
  
• Practice in conversation: Try saying it in sentences about your close friends.
  
• Pair with synonyms: Like “inseparable” or “best friends” to reinforce meaning.
  

By repeating these steps, ESL learners can use this idiom confidently in both spoken and written English.

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FAQs About “As Thick as Thieves”

1. What does “as thick as thieves” mean in simple words?
It means two or more people are extremely close friends who trust and support each other completely.

2. Can I use “as thick as thieves” for family members?
Yes! It works for friends, siblings, or relatives who share a strong bond.

3. Is it formal English?
No, it’s idiomatic and conversational, better for informal writing or speaking.

4. Can I change the words in the phrase?
No, altering the phrase breaks the idiom. Always use exactly “as thick as thieves”.

5. What is a synonym for “as thick as thieves”?
Some alternatives are inseparable, best friends, bosom buddies, and joined at the hip.

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Conclusion

The idiom “as thick as thieves” is a vibrant, friendly way to describe people who share deep friendship, loyalty, and trust. Its roots go back centuries, but today it’s a versatile and widely understood expression.

For ESL learners and non-native speakers, mastering this phrase can enhance conversational English, add idiomatic flair, and make speaking or writing sound natural and engaging.

Remember: always use the phrase exactly as it is, pair it with real-life examples, and practice it in everyday situations. By doing so, you’ll speak like a confident native speaker, and your conversations will shine with authenticity.