Skip to content
Free standard shipping to supported destinations
Delta-Xi LogoDelta Xi
ShopOur storyLearnHelp
Learn
OverviewConcepts
Delta-Xi LogoDelta Xi

A place for good ideas, on a shirt or off the page.

Say hello

Explore

  • Shop all
  • Mathematics T-shirts
  • Accessories
  • Learn
  • Our story

Here to help

  • Contact
  • Size & care questions
  • Shipping & returns
  • Your orders
  • Track an order

Keep in touch

  • Instagram
  • Discord
  • Telegram
  • Affiliate programme

© 2026 Delta Xi. Prices in USD.

PrivacyTerms

Your cookie choices

Essential cookies keep your basket and sign-in working. Optional cookies help us understand visits and measure ads. Privacy details.

STEM Concepts

Follow an equation, work through an example, or check an assumption. Browse 69 concepts across mathematics, physics and computing.

All📐Mathematics(19)⚛️Physics(12)🔄Algorithms(7)🏗️Data Structures(8)🤖Machine Learning(10)🧠CS Theory(5)🖥️Systems(2)🌐Networking(3)⚙️Engineering(2)🧪Chemistry(1)
🧠

theory

CS Theory

Halting Problem

The undecidable problem of determining whether a program will finish or run forever.

View Explanation
🧠

theory

CS Theory

NP-Completeness

Class of problems that are both in NP and NP-hard, representing the hardest problems in NP.

View Explanation
🧠

theory

CS Theory

P vs NP Problem

The most important open problem in computer science: can every quickly verifiable solution be quickly found?

View Explanation
H(X)=−∑xp(x)log⁡2p(x)H(X)=-\sum_x p(x)\log_2 p(x)H(X)=−x∑​p(x)log2​p(x)
CS Theory

Shannon entropy

Measure uncertainty in a set of possible messages.

View Explanation
🧠

theory

CS Theory

Turing Machine

Abstract mathematical model of computation that defines what is computable.

View Explanation