OpenAI's GPT-5 represents a significant advancement over its predecessor GPT-4 in several key areas:

Intelligence and Reasoning:

GPT-5 is described as the first model that truly feels like conversing with a PhD-level expert, surpassing GPT-4's college-level capability.

It integrates reasoning and fast-response capabilities into a unified model, with a real-time router that dynamically decides when to engage deeper reasoning.

The model handles multi-step logic and complex decision-making more effectively than GPT-4.

Accuracy and Hallucinations:

GPT-5 significantly reduces hallucinations (fabricated or incorrect responses), with rates 26%-65% lower than GPT-4 and earlier models.

It better identifies tasks it cannot complete and avoids speculation, improving trustworthiness.

In healthcare-related queries, it hallucinates only about 1.6% of the time, compared to over 12-15% in previous models.

Performance and Speed:

GPT-5 is faster and more efficient, managing complex queries with less resource consumption.

It scores higher on coding benchmarks (e.g., SWE-bench Verified with 74.9%) than competitors and previous generations.

Enhanced training techniques with a larger, more diverse dataset and possibly a more advanced architecture (graph neural networks with attention mechanisms) improve its processing and contextual understanding.

Multilingual and Nuanced Language:

GPT-5 supports more languages with better accuracy and fluency.

It understands and generates more nuanced language, including sarcasm, irony, and complex constructs.

User Experience and Safety:

GPT-5 simplifies the user experience by eliminating confusing model selection steps.

It introduces "Safe Completions," allowing it to respond safely to potentially risky queries by providing high-level information rather than outright refusing.

Extensive safety assessments (5,000 hours) have been conducted to minimize harmful outputs.

Applications:

GPT-5 excels in writing, programming, healthcare, education, and other specialized professional tasks.