h

• 英语字母表的第八个字母，为辅音字母。通常表示清声门擦音 /h/，在一些方言中常脱落。也用作化学元素氢的符号、小时、高度、序列或类别中第八个的标记。

The eighth letter of the English alphabet and the sixth consonant, representing the voiceless glottal fricative sound /h/. As a grapheme, 'H' is produced by exhaling air through an open glottis without vibration of the vocal cords. It is a letter frequently subject to elision in certain English dialects, where it is dropped entirely in words like 'herb' (American English) or 'hour'. It functions as a designation for the eighth item in a sequence, a chemical symbol for hydrogen, an abbreviation for height or hour, and a classification category.

1. The eighth letter of the English alphabetA1formal

   The uppercase or lowercase character (H, h) that constitutes the eighth symbol in the Latin-based English alphabet, classified as a consonant. It represents a voiceless glottal fricative produced by a gentle exhalation with the vocal cords held apart. The pronunciation of its name, 'aitch', is a notable exception to typical letter names as it begins with a vowel rather than the consonant it represents. In some dialects, particularly Cockney and certain regional British accents, the /h/ sound is frequently dropped in speech.

   英文字母第八个字母

   • The word 'house' begins with the letter H.
   • She pronounces the H in 'herb', unlike most Americans.
   • The silent H in 'hour' can confuse English learners.
   • He wrote a capital H with two vertical lines connected by a horizontal bar.
   • Dropping one's H's is a feature of Cockney dialect.

2. The chemical symbol for hydrogenB1formalscientific

   The one-letter chemical symbol representing the element hydrogen, atomic number 1 on the periodic table. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all baryonic mass. It is a colorless, odorless, highly flammable diatomic gas (H₂) at standard temperature and pressure and serves as a crucial component in water, organic compounds, and potential clean energy sources.

   氢的化学符号

   • Water has the chemical formula H₂O, containing two H atoms.
   • Hydrogen, symbolized by H, is the lightest element on the periodic table.
   • The Hindenburg disaster highlighted the dangers of using H as a lifting gas.
   • Green H produced from renewable energy is a promising clean fuel.
   • The sun fuses H into helium through nuclear fusion.

3. An abbreviation for hour or hoursA1formal

   The letter H used as a standard abbreviation or symbol for the unit of time known as an hour, equal to 60 minutes or 3,600 seconds. This notation is commonly employed in timetables, schedules, scientific measurements, digital clocks, business operating hours, and technical specifications where the lowercase 'h' indicates the duration of time, especially in the metric-styled format (e.g., km/h for kilometers per hour).

   小时，时间单位

   • The store's opening hours are 9 h to 17 h on weekdays.
   • The speed limit on the highway is 120 km/h.
   • The event is scheduled to last approximately 3 h.
   • She earns $15/h at her part-time job.
   • The flight duration was listed as 8 h 45 min.

4. The eighth item in a sequence or classificationA2formal

   A designation used to mark the eighth position, item, or category within a structured sequence, directly following G. It is frequently applied in outlines, options in multiple-choice tests, hierarchical grading systems, sizing charts, and row or section labeling in venues. Being the eighth letter, it occupies the midpoint of the standard 26-letter English alphabet.

   序列或分类中的第八项

   • Our seats are in Row H, which offers a great view of the stage.
   • The multiple-choice question included Options F, G, H, and I.
   • The company classifies H-tier customers as the highest priority.
   • Section H of the report contains the financial projections.
   • The recipe's Step H involves letting the dough rise for an hour.

5. An abbreviation for height in measurementA2formal

   The letter H used as a standard abbreviation for height or vertical dimension in architectural plans, engineering drawings, mathematical formulas, medical charts, and everyday shorthand. It frequently appears in product specifications, clothing size guides, health records, and geometry, where it denotes the perpendicular distance from the base to the top of an object, person, or shape.

   高度（缩写）

   • The box dimensions are listed as W 50cm x H 75cm x D 40cm.
   • Her height is recorded as H: 165 cm on the medical chart.
   • The formula for the area of a triangle is 1/2 × b × h.
   • The architect labeled the ceiling h at 3 meters on the plan.
   • Enter your height in the field marked H on the application form.