The Apple Watch Series 4 (44mm) was a significant step forward when it was released in September 2018. Here's what you need to know about it:  

Key Features:

• Larger Display: Compared to previous generations, the Series 4 featured a significantly larger, edge-to-edge OLED Retina display with Force Touch. The 44mm version has a resolution of 368 x 448 pixels with a display area of 977 sq mm.  
• S4 Chip: It was powered by the S4 dual-core processor, which offered up to 2x faster performance compared to the Series 3. It also included the W3 Apple wireless chip.  
• Health and Safety:
  • Electrical Heart Sensor (ECG): A groundbreaking feature at the time, allowing users to take an electrocardiogram directly from their wrist (region dependent on software availability).  
  • Optical Heart Sensor (2nd generation): For more accurate heart rate monitoring, including high and low heart rate notifications and irregular rhythm notifications.  
  • Fall Detection: Utilizing an improved accelerometer and gyroscope, the watch could detect hard falls and initiate an Emergency SOS call if the user remained unresponsive.  
  • Emergency SOS: Allowed users to quickly call for help.  
• Design: Featured a thinner design with more rounded corners. The Digital Crown had haptic feedback for a more tactile experience.  
• Water Resistance: Rated for 50 meters (ISO standard 22810:2010), making it suitable for swimming and shallow-water activities.  
• Connectivity:
  • GPS, GLONASS, Galileo, and QZSS for location tracking.  
  • Wi-Fi: 802.11b/g/n 2.4GHz.  
  • Bluetooth 5.0.
  • Optional Cellular (GPS + Cellular models): Allowed for calls, messages, and data without needing an iPhone nearby (requires a cellular plan).  
• Storage: 16GB of internal storage.
• Speaker and Microphone: The speaker was 50 percent louder than the previous generation, and it had a microphone for calls and Siri.  
• watchOS 5: Launched with watchOS 5, which introduced features like automatic workout detection, Walkie-Talkie, and more. It is upgradable to newer versions of watchOS (up to watchOS 10.6.1).
• Battery Life: Up to 18 hours of battery life on a single charge (usage dependent).

Specifications of the Apple Watch Series 4 (44mm):

• Case Size: 44mm (44mm height, 38mm width, 10.7mm depth)  
• Case Materials: Available in Aluminum (Silver, Space Gray, Gold) and Stainless Steel (Silver, Space Black (DLC), Gold (PVD)).  
• Display: LTPO OLED Retina display with Force Touch, 368 by 448 pixels.  
• Chip: S4 with 64-bit dual-core processor, W3 Apple wireless chip.  
• Memory: 1GB RAM.  
• Storage: 16GB.
• Connectivity: GPS, GLONASS, Galileo, QZSS, Wi-Fi (802.11b/g/n), Bluetooth 5.0, optional LTE and UMTS.
• Water Resistance: 50 meters.  
• Battery: Built-in rechargeable lithium-ion battery (up to 18 hours).  
• Weight:
  • Aluminum Case: 36.7g  
  • Stainless Steel Case: 47.9g