Hexagram (I Ching)

The I Ching book consists of 64 hexagrams.
A hexagram in this context is a figure composed of six stacked horizontal lines, where each line is either Yang or Yin. The hexagram lines are traditionally counted from the bottom up, so the lowest line is considered line one, while the top line is line six. Hexagrams are formed by combining the original eight trigrams in different combinations. Each hexagram is accompanied with a description, often cryptic, akin to parables. Each line in every hexagram is also given a similar description.
The Chinese word for a hexagram is 卦 "guà", although that also means trigram.

Types

Classic and modern I Ching commentaries mention a number of different hexagram types:

Eight Trigrams
Original Hexagram
Future Hexagram
Contrasting Hexagram
Complementary Hexagram
Hexagram of Sequence
Nuclear Hexagram
Hexagram of Change
Internal Hexagram
External Hexagram

Sequences

The most commonly known sequence is the King Wen sequence. A totally different sequence was found in the Mawangdui Silk Texts. The hexagrams are also found in the Binary sequence, also known as Fu Xi sequence or Shao Yong sequence.

Lookup table

Upper → Lower ↓	☰	☱	☲	☳	☴	☵	☶	☷
Upper → Lower ↓	乾	兌	離	震	巽	坎	艮	坤
Upper → Lower ↓	Heaven	Lake	Flame	Thunder	Wind	Water	Mountain	Earth
☰	1	43	14	34	9	5	26	11
☰	䷀	䷪	䷍	䷡	䷈	䷄	䷙	䷊
乾	乾	夬	大有	大壯	小畜	需	大畜	泰
Heaven	Force	Displacement	Great Possessing	Great Invigorating	Small Harvest	Attending	Great Accumulating	Pervading
☱	10	58	38	54	61	60	41	19
☱	䷉	䷹	䷥	䷵	䷼	䷻	䷨	䷒
兌	履	兌	睽	歸妹	中孚	節	損	臨
Lake	Treading	Open	Polarising	Converting the Maiden	Inner Truth	Articulating	Diminishing	Nearing
☲	13	49	30	55	37	63	22	36
☲	䷌	䷰	䷝	䷶	䷤	䷾	䷕	䷣
離	同人	革	離	豐	家人	既濟	賁	明夷
Flame	Concording People	Skinning	Radiance	Abounding	Dwelling People	Already Fording	Adorning	Intelligence Hidden
☳	25	17	21	51	42	3	27	24
☳	䷘	䷐	䷔	䷲	䷩	䷂	䷚	䷗
震	无妄	隨	噬嗑	震	益	屯	頤	復
Thunder	Innocence	Following	Gnawing Bite	Shake	Augmenting	Sprouting	Swallowing	Returning
☴	44	28	50	32	57	48	18	46
☴	䷫	䷛	䷱	䷟	䷸	䷯	䷑	䷭
巽	姤	大過	鼎	恆	巽	井	蠱	升
Wind	Coupling	Great Exceeding	Holding	Persevering	Ground	Welling	Correcting	Ascending
☵	6	47	64	40	59	29	4	7
☵	䷅	䷮	䷿	䷧	䷺	䷜	䷃	䷆
坎	訟	困	未濟	解	渙	坎	蒙	師
Water	Arguing	Confining	Before Completion	Deliverance	Dispersing	Gorge	Enveloping	Leading
☶	33	31	56	62	53	39	52	15
☶	䷠	䷞	䷷	䷽	䷴	䷦	䷳	䷎
艮	遯	咸	旅	小過	漸	蹇	艮	謙
Mountain	Retiring	Conjoining	Sojourning	Small Exceeding	Infiltrating	Limping	Bound	Humbling
☷	12	45	35	16	20	8	23	2
☷	䷋	䷬	䷢	䷏	䷓	䷇	䷖	䷁
坤	否	萃	晉	豫	觀	比	剝	坤
Earth	Obstruction	Clustering	Prospering	Providing-For	Viewing	Grouping	Stripping	Field